CONGRESS OF THE UNITED STATES

CONGRESSIONAL BUDGET OFFICE

CBO

Policy Options 

for 

Unmanned 

Aircraft Systems

JUNE 2011
Pub. No. 4083
The Congress of the United States O Congressional Budget Office

A

STUDY

CBO

Policy Options for 

Unmanned Aircraft Systems

June 2011
CBO

Notes

Unless otherwise specified, all years referred to in this study are federal fiscal years (which run 

from October 1 to September 30), and costs are expressed in 2011 dollars of total obligational 

authority.

The costs and quantities in the services’ acquisition plans for unmanned aircraft systems 

are from the Department of Defense’s budget request for 2012, Selected Acquisition Reports 

for December 2010, and Aircraft Procurement Plan: Fiscal Years 2012–2041 (submitted with 

the 2012 budget, March 2011). CBO adjusted the services’ cost data using its projection of 

inflation.

This study includes only unclassified unmanned aircraft systems.

Photos on the cover were provided by the U.S. Army and the U.S. Air Force. The top photo 

shows an MQ-9 Reaper parked in a hangar. The lower-left photo shows an image of 

earthquake damage in Haiti taken by a Global Hawk. The lower-right photo shows a typical 

simulator at a ground station for unmanned aircraft.
Preface

CBO

Unmanned aircraft systems have long held great promise for military operations, but 

technology has only recently matured enough to exploit that potential. Much as the stealth 

fighter and Patriot missile came to public attention during the 1991 Gulf War, surveillance 

and missile-attack operations by Predator unmanned aircraft have been well publicized 

throughout the more recent conflicts in Iraq and Afghanistan. The Department of Defense’s 

(DoD’s) 2012 plan calls for purchasing more of the existing unmanned aircraft systems for 

current operations, improving the systems already in service, and designing more-capable 

unmanned aircraft systems for the future. At the request of the former chairman of the House 

Committee on the Budget, the Congressional Budget Office (CBO) compared the costs of 

DoD’s plans and the capabilities those plans might provide for reconnaissance and light attack 

missions with the costs and capabilities of some alternative options. In keeping with CBO’s 

mandate to provide objective, impartial analysis, this study makes no recommendations.

Bernard Kempinski of CBO’s National Security Division prepared the study, with assistance 

from David Arthur, under the supervision of David Mosher and Matthew Goldberg. 

Alec Johnson assisted with data collection, and Christopher Murphy helped fact-check the 

document. The artwork in Summary Figures 1 through 3, Figure 1-1, and the figure in 

Box 1-1 was done by Bernard Kempinski. Nathan Musick and David Newman, both of 

CBO, and William R. Thissell of Lanmark Technology, Inc., provided thoughtful comments. 

(The assistance of external reviewers implies no responsibility for the final product, which 

rests solely with CBO.)

Amanda Balestrieri edited the study, with assistance from Sherry Snyder, and Chris Howlett 

proofread it. Maureen Costantino and Jeanine Rees prepared the graphics and page layout, 

and Maureen Costantino designed the cover. Monte Ruffin printed the initial copies, and 

Linda Schimmel coordinated the print distribution. The report is available on CBO’s Web 

site (www.cbo.gov).

Douglas W. Elmendorf

Director

June 2011

Contents

CBO

Summary vii

1 Existing Unmanned Aircraft Systems and Future Plans 1

Missions 2

Existing Systems 3

Future Plans 5

2 Assessing Policy Options 15

Options for the Air Force 16

Options for the Army 19

Appendix: Missions Conducted by Unmanned Aircraft Systems and 

Reasons for Using Them 27

Glossary 33
CONTENTS POLICY OPTIONS FOR UNMANNED AIRCRAFT SYSTEMS VI

CBO

Tables

S-1. Acquisition Cost of Medium-Sized and Large Unmanned Aircraft Systems 

Under the Department of Defense’s 2012 Plan ix

S-2. Overview of Options for the Air Force and the Army and Their Cost 

Relative to the Department of Defense’s 2012 Plan xi

1-1. Characteristics of Medium-Sized and Large Unmanned Aircraft Systems 

Fielded or Under Development 4

1-2. Quantity and Cost of Acquisitions Under the Air Force’s 2012 Plan 7

1-3. Quantity and Cost of Acquisitions Under the Army’s 2012 Plan 12

1-4. Quantity and Cost of Acquisitions Under the Navy and Marine Corps’ 2012 Plan 13

2-1. Differences Between Options for the Air Force and Its 2012 Plan, 2011 to 2020 18

2-2. Differences Between Options for the Army and Its 2012 Plan, 2011 to 2020 20

Figures

S-1. Medium-Sized and Large Unmanned Aircraft Designed for Conducting 

Reconnaissance and Attacking Ground Targets viii

S-2. Change in Capability at Different Ranges and in Acquisition Cost in 2020 

Under CBO’s Options for the Air Force xiii

S-3. Change in Capability at Different Ranges and in Acquisition Cost in 2020 

Under CBO’s Options for the Army xv

1-1. Missions Performed by Unmanned Aircraft, by Altitude and Endurance 2

1-2. Acquisition Cost of Medium-Sized and Large Unmanned Aircraft Systems and of 

All Systems Under the Department of Defense’s 2012 Plan 6

1-3. Inventory of Medium-Sized and Large Unmanned Aircraft Under the 

Department of Defense’s 2012 Plan 10

1-4. Payload-Duration at Various Ranges Under the Air Force’s 2012 Plan 11

1-5. Payload-Duration at Various Ranges Under the Army’s 2012 Plan 13

1-6. Payload-Duration at Various Ranges Under the Navy and Marine Corps’ 2012 Plan 14

2-1. Methods of Controlling Unmanned Aircraft Systems in a Combat Theater 24

Box

1-1. Payload-Duration as a Comparative Measure of Capability 8
CBO

Summary

Over the next 10 years, the Department of 

Defense (DoD) plans to purchase about 730 new 

medium-sized and large unmanned aircraft systems based 

on designs currently in operation, while also improving 

the unmanned aircraft already in service. By the Congressional Budget Office’s (CBO’s) estimates, completing the 

investments in systems for which there are detailed plans 

will require about $36.9 billion through 2020. 

CBO has analyzed eight alternatives to DoD’s fiscal year 

2012 plan for expanding its fleet of medium-sized and 

large unmanned aircraft that are designed for reconnaissance and light attack missions. This study presents each 

alternative’s likely effect on forcewide capability and 

acquisition costs. The alternatives—three for the Air 

Force and five for the Army—would change the mix of 

unmanned aircraft systems that are in or nearing production, the way that unmanned systems are assigned to 

units and operated in geographic areas where units are 

deployed, or both. The costs of those options would 

range from $3.7 billion less than DoD’s plan through 

2020 to $2.9 billion more. They would provide capability in several important dimensions ranging below and 

above that of the planned fleet.

Existing Systems and Future Plans

DoD currently has more than 6,000 unmanned aircraft. 

The majority of those aircraft are short-range reconnaissance systems that have a wingspan of a few feet and have 

handheld controls used by small military units in combat 

to look “around corners” or “over hills.” Spending for 

those systems represents a relatively small proportion of 

the total investment planned for unmanned aircraft 

systems. The bulk of DoD’s planned spending is for the 

more costly medium-sized and large unmanned aircraft 

systems that are designed to conduct reconnaissance 

missions or attack ground targets (see Summary 

Figure 1). 

The armed services have developed detailed procurement 

plans, including estimated quantities and costs, for the 

unmanned aircraft systems that are in or nearing production.1

 Those plans would increase the inventory of the 

aircraft by 35 percent over the next 10 years. DoD also 

is investing in research and development for the next 

generation of more technologically advanced unmanned 

aircraft, which will provide improved reconnaissance and 

attack capabilities and will broaden the types of missions 

that can be accomplished. As the funding required for 

near-term systems begins to decline after 2015, funding 

for the next generation of unmanned aircraft will probably increase. Analyzing the longer-term plans will not be 

possible until they are defined in more detail. 

The Air Force’s Plans

The Air Force currently operates at least four mediumsized or large unmanned aircraft: Global Hawks, 

Predators, Reapers, and Sentinels. The largest aircraft is 

the jet-powered RQ-4 Global Hawk, and the Air Force 

has 14 of them, according to CBO’s information. The 

most numerous, at approximately 175 aircraft, is the 

MQ-1 Predator, a piston-engine propeller aircraft that 

can take still or video imagery and shoot Hellfire missiles. 

A larger version of the Predator, the turboprop-powered 

MQ-9 Reaper, is beginning to enter the force, and about 

40 have been delivered as of 2011. (The “MQ-” designation for the Predator and Reaper identify them as multimission aircraft capable of reconnaissance and attack 

1. The costs and quantities in the services’ acquisition plans for 

unmanned aircraft systems are CBO estimates based on data from 

the Department of Defense’s budget request for fiscal year 2012, 

Selected Acquisition Reports for December 2010, and Aircraft 

Procurement Plan: Fiscal Years 2012–2041 (submitted with the 

2012 budget, March 2011). CBO adjusted the costs using its 

projection of inflation.
VIII POLICY OPTIONS FOR UNMANNED AIRCRAFT SYSTEMS

CBO

Summary Figure 1.

Medium-Sized and Large Unmanned Aircraft Designed for Conducting 

Reconnaissance and Attacking Ground Targets

Source: Congressional Budget Office.

Note: All aircraft are drawn to the same scale. The silhouette figure is a 6-foot-tall soldier, also drawn to scale.

a. The MQ-SX is a notional unmanned aircraft system based on existing aircraft systems that is more capable than the Predator class in 

speed and altitude and less capable than the Global Hawk class. The illustration shows relative size but does not represent the actual 

design of the notional aircraft.

RQ-4 Global Hawk/

Broad Area Maritime Surveillance

Feet

MQ-8 Firescout

0 10 20 30 40 50

MQ-1C Grey Eagle

MQ-1 Predator

MQ-SXa

RQ-7 Shadow

MQ-5 Hunter

MQ-9 Reaper
SUMMARY POLICY OPTIONS FOR UNMANNED AIRCRAFT SYSTEMS IX

CBO

Summary Table 1.

Acquisition Cost of Medium-Sized and Large Unmanned Aircraft Systems 

Under the Department of Defense’s 2012 Plan 

(Millions of 2011 dollars)

Source: Congressional Budget Office based on data from the Department of Defense’s budget request for 2012, Selected Acquisition

Reports for December 2010, and Aircraft Procurement Plan: Fiscal Years 2012–2041 (submitted with the 2012 budget, 

March 2011). 

Note: Acquisition cost includes the cost of procuring air vehicles, sensors, and ground stations, plus the cost for research, development, 

test, and evaluation. The services’ cost data have been adjusted using CBO’s projection of inflation and rounded to the nearest

$10 million.

a. The Department of Defense has no plans to acquire or modify the specified system in these years.

b. The cost is for the follow-on aircraft the Air Force plans to acquire instead of the Reaper.

missions.) The RQ-170 Sentinel is a stealthy reconnaissance aircraft whose existence has only recently been 

acknowledged by the Air Force. Most performance 

characteristics of the Sentinel remain classified.

The Air Force’s near-term goals are to increase the number of Global Hawk and Reaper aircraft that can be 

continuously and simultaneously operated. To meet that 

goal, the Air Force plans to purchase 288 Reapers (48 per 

year from 2011 through 2016) and 28 Global Hawks 

from 2011 through 2018. Documents provided to the 

Congress by DoD indicate plans to continue purchasing 

multimission unmanned aircraft after 2016, although 

the type of aircraft is not specified.2

 On the basis of the 

information available, CBO assumed that the Air Force’s 

purchases after 2016 would continue at 48 aircraft per 

year and would comprise either additional Reapers or a 

follow-on aircraft with range, payload, and cost similar to 

the Reaper. (Unless making a distinction is necessary, 

references to the Reaper in this study pertain to both the 

Reaper itself and the possible follow-on system.) The 

Air Force is also exploring the characteristics that would 

be desired in a larger aircraft a generation beyond the 

Global Hawk.

About $20.4 billion will be needed for the aircraft the Air 

Force plans to purchase through 2020, CBO estimates: 

$7.3 billion for Global Hawks and $13.1 billion for 

Reapers and their follow-on (see Summary Table 1). 

Costs would average about $2.0 billion per year through 

2020. 

Total,

2011-

2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2020

RQ-4 Global Hawk 1,200 1,060 890 790 810 710 1,160 530 80 60 7,290

MQ-1 Predator 30 10 10 10 a a a a a a 60

MQ-9 Reaper 1,700 1,550 1,740 1,440 1,350 1,150 1,060 b 1,040 b 1,030 b 1,010 b 13,070

MQ-1C Grey Eagle 870 1,060 1,040 740 220 90 a a a a 4,020

RQ-7 Shadow 610 250 270 200 300 280 a a a a 1,910

RQ-4 Broad Area Maritime Surveillance 530 560 760 880 900 1,010 1,230 1,260 1,130 1,130 9,390

MQ-8 Firescout 60 70 60 80 80 90 130 160 150 150 1,030

RQ-7 Shadow 90 10 10 10 a a a a a a 120

Total 5,090 4,570 4,780 4,150 3,660 3,330 3,580 2,990 2,390 2,350 36,890

Air Force

Army 

Navy and Marine Corps

All Services

2. Department of Defense, Aircraft Procurement Plan: Fiscal Years 

2012–2041 (submitted with the 2012 budget, March 2011).
X POLICY OPTIONS FOR UNMANNED AIRCRAFT SYSTEMS

CBO

The Army’s Plans

The Army currently operates three medium-sized 

unmanned aircraft systems: Hunters, Shadows, and 

Predators. Overall, the Army’s inventory includes about 

20 MQ-5B Hunters (older aircraft scheduled for retirement by 2013), about 450 RQ-7 Shadows, and about 

40 MQ-1 Predators in two versions (specifically, MQ-1 

Warrior Alphas and MQ-1C Grey Eagles).3

Over the next five years, the Army plans to purchase 

20 Shadows to replace losses, upgrade the existing 

Shadows with tactical data links and a laser targeting 

system, and purchase 107 more of the medium-altitude 

Grey Eagles. CBO estimates that those plans will cost 

about $5.9 billion: $1.9 billion for the Shadows and 

$4.0 billion for the additional Grey Eagles. In the longer 

term, the Army is exploring concepts for an aircraft that 

has greater endurance (that is, can stay in the air for a 

longer time). It also may decide to resume efforts to 

increase the capabilities of unmanned aircraft used by 

combat brigades; those plans were shelved when the 

Army’s Future Combat System was canceled in 2009.

The Navy and Marine Corps’ Plans

The Navy is currently testing two new types of aircraft 

that it hopes to field in the near future—the longendurance Broad Area Maritime Surveillance (BAMS) 

aircraft, which is a Global Hawk variant optimized for 

naval operations, and the MQ-8B Firescout unmanned 

helicopter. The Navy plans to purchase 36 BAMS aircraft 

at a cost of about $9.4 billion by 2020 and operate them 

from a few bases worldwide to provide surveillance of 

activities on the oceans. The Navy also plans to purchase 

61 Firescouts by 2020 at a cost of $1.0 billion; those helicopters will be based on selected surface ships and will 

provide local reconnaissance and the capability to attack 

hostile surface targets. The Navy’s plans call for purchasing a total of 65 BAMS through 2026 and 168 Firescouts 

through 2028.

The Marine Corps is in the process of fielding the 

Shadow to support ongoing operations in Southwest 

Asia. Thirteen systems (with four aircraft per system) had 

been delivered by the end of calendar year 2009. The 

Marine Corps does not plan to purchase additional 

Shadow systems but instead will spend about $120 million to upgrade some Shadows already in its inventory. 

In the longer term, the Navy is exploring concepts for a 

carrier-based unmanned aircraft, called the Unmanned, 

Carrier-Launched Airborne Surveillance and Strike aircraft, and is currently flying a demonstrator aircraft to 

help develop the technologies and procedures needed to 

operate such an aircraft. The Marine Corps is exploring 

concepts for a medium-sized system (currently referred to 

as the Group 4 Unmanned Aircraft System) that would 

be designed to perform various missions in support of 

amphibious operations. Both systems might enter service 

by 2020.

Assessing Policy Options

The Congressional Budget Office examined the implications—both for the capabilities of the armed forces and 

for DoD’s acquisition budget—of eight possible alternatives to DoD’s fiscal year 2012 plan (three for the Air 

Force and five for the Army). Acquisition cost includes 

the cost of procuring an unmanned aircraft system (the 

aircraft, sensors, and ground stations), plus the cost of 

research, development, test, and evaluation. 

The options would alter DoD’s acquisition plans through 

2020 (see Summary Table 2). Three of the options would 

improve capabilities—as measured by the weight the fleet 

of aircraft can carry (its payload) and the time the aircraft 

will be able to remain in the air (its endurance)—for the 

same cost as DoD’s plans. Two options would improve 

capabilities but would also increase acquisition cost, and 

three options would reduce cost but would also yield 

some reduction in capabilities. 

The options are meant to illustrate the cost implications 

of different approaches to enhancing capabilities and are 

not designed to reach any specific goal or to counter any 

specific adversaries that might arise in the future. CBO 

did not examine longer-term options requiring significant technological development because the uncertainty 

surrounding what could be fielded and what might be 

needed is too great for a detailed analysis. Nor did CBO 

examine options for the Navy and Marine Corps—not 

only because those services will have relatively few 

unmanned aircraft systems in the near term but also to 

keep the number of options to a manageable level. In 

addition, this study does not assess the operation and 

support costs of the options. In CBO’s estimation, those 

costs would change little in the eight options because

3. In August 2010, the Army adopted Grey Eagle as the official 

name for the General Atomics MQ-1C. Earlier, the Army had 

called the system the Extended Range Multi-Purpose (ER/MP) 

and Sky Warrior. The MQ-1 Warrior Alpha is essentially the same 

as the Air Force’s Predator.
SUMMARY POLICY OPTIONS FOR UNMANNED AIRCRAFT SYSTEMS XI

CBO

Summary Table 2.

Overview of Options for the Air Force and the Army and Their Cost 

Relative to the Department of Defense’s 2012 Plan

Source: Congressional Budget Office.

a. The MQ-SX is a notional unmanned aircraft system based on existing aircraft systems that is more capable than the Predator class in 

speed and altitude and less capable than the Global Hawk class.

b. In remote-split operations, deployed divisions would have operational control of aircraft from a central fleet rather than be equipped with 

their own aircraft.

most of the options would require only modest changes 

in the number of personnel—a major contributor to 

those costs—and because differences in fuel consumption 

and the cost of spare parts probably would be minimal.4

To compare the capability that could be expected under 

the options, CBO calculated an aggregate measure—the 

payload-duration—for each aircraft. Payload-duration is 

the weight (payload) that an unmanned aircraft could 

carry to a location, multiplied by the amount of time the 

aircraft could be kept there on orbit (duration). In this 

case, “on orbit” means that the unmanned aircraft is circling the target area continuously.5

CBO calculated payload-duration for individual aircraft 

at orbits positioned at various distances from where the 

aircraft are based. The distance, or range, to the orbit 

affects duration: The farther the mission is located from 

where the aircraft is launched, the less time the aircraft 

will be able to remain at the target location. The aircraft’s 

endurance and speed also affect duration: The faster the 

aircraft can travel, the more time it can spend at the target 

location. Payload capacity serves as a simplified measure 

of the types and quality of sensors and weapons that an 

aircraft could carry—under the general assumption that, 

all else being equal, a greater payload capacity enables the 

aircraft to carry more-capable sensors and a greater number or variety of weapons. The total payload-duration of 

all aircraft in the force captures the effects of aircraft 

inventory, transit speed, endurance, and payload capacity. 

Payload-duration better captures reconnaissance capability than does the number of orbits because it incorporates 

the capacity of the aircraft to carry equipment and to 

spend time on reconnaissance missions.

Approach Option

Buy New, Stealthier Aircraft 1. Buy 224 MQ-SXs and 336 Fewer Reapersa 0

2. Buy 336 MQ-SXs and 336 Fewer Reapersa 2.9

3. Buy 24 MQ-SXs and 24 Fewer Global Hawksa -3.7

Buy More-Capable Aircraft 4. Buy 69 Reapers and 78 Fewer Grey Eagles 0

5. Buy 78 Reapers and 78 Fewer Grey Eagles 0.5

Buy More, Less-Expensive Aircraft 6. Buy 350 Firescouts and 78 Fewer Grey Eagles 0

Change the Way Aircraft Are Operated by 7. With 42 Fewer Grey Eagles -1.3

Conducting Remote-Split Operationsb 8. With 36 Reapers and 78 Fewer Grey Eagles -1.0

DoD's 2012 Plan

(Billions of 2011 dollars)

Air Force

Army

Cost Relative to

4. Some options would require modest changes in the number of 

personnel. Option 6 for the Army, for example, would increase 

the number of unmanned aircraft operators, but CBO assumed 

that the Army would provide those people from existing ranks, as 

it has done when adopting other unmanned aircraft systems. Conversely, Options 7 and 8 would require fewer personnel, but those 

savings are not included in CBO’s analysis. 

5. The orbit may also be called a continuous, persistent, or loitering 

orbit, in which the aircraft remains on station, waiting for orders 

to perform a required mission. In military parlance, an aircraft 

orbit is known as a combat air patrol, or CAP.
XII POLICY OPTIONS FOR UNMANNED AIRCRAFT SYSTEMS

CBO

Options for the Air Force

CBO’s options for the Air Force examine the implications 

of more quickly developing and fielding a new aircraft 

that would have improved payload-duration plus other 

characteristics such as a lower chance of being detected 

(stealth) and higher speed—traits that would be advantageous in conflicts against technologically capable 

adversaries. 

Under the options, the Air Force would purchase a 

notional MQ-SX—an aircraft that would have some 

characteristics consistent with those the Air Force is considering for its proposed MQ-X—in lieu of some of the 

Reapers or Global Hawks in current plans. The MQ-SX 

postulated by CBO would be a jet-powered aircraft about 

one and a half times the size of the Reaper with an airframe designed to be more difficult to detect and target 

by air-defense systems. Relative to the Reaper, the larger 

size of the MQ-SX would enable it to carry a greater payload (sensors, weapons, or fuel); jet power would allow 

the aircraft to reach its destination (a target or orbit location) in less time; and stealth features would improve 

its ability to operate in defended airspace.6

 CBO’s cost 

estimate for the notional MQ-SX assumes modest 

improvements in stealth relative to that of Global Hawks, 

Predators, and Reapers. A highly stealthy design would 

probably cost more.

Option 1—Buy 224 MQ-SXs and 336 Fewer Reapers 

(Same Cost). Instead of purchasing 480 Reapers, the Air 

Force would buy only 114 (336 fewer) and would also 

buy 224 MQ-SX aircraft to arrive at the same overall 

acquisition cost as its current plan. Although the option 

would yield a smaller inventory of multimission 

unmanned aircraft, the force’s total payload-duration 

would remain about the same relative to current plans 

for orbits at short range because the speed and payload 

advantage of the MQ-SX would compensate for the 

smaller inventory (see Summary Figure 2). Payloadduration would improve about 35 percent relative to 

current plans at intermediate ranges (1,500 nm) by 2020 

because the higher speed of the MQ-SX would increase 

the proportion of time it could spend on station relative 

to the slower Reaper. Payload-duration would be 

unchanged at long range (2,500 nm) because only the 

Global Hawk has significant capability at that range. 

Option 2—Buy 336 MQ-SXs and 336 Fewer Reapers 

(Higher Cost). The Air Force would substitute purchases 

of 336 Reapers with 336 MQ-SXs. The number of 

aircraft purchased each year would remain almost 

unchanged through 2020 but would shift from all 

Reapers in 2011 to all MQ-SXs by 2015. Relative to the 

Air Force’s 2012 plan, the total cost would increase by 

about $2.9 billion because the MQ-SX would be more 

expensive than the Reaper. Although the Air Force’s total 

inventory of MQ-type unmanned aircraft systems would 

remain essentially unchanged under this option, the 

larger size and higher speed of the MQ-SX relative to 

the Reaper would result in a force capable of maintaining 

a payload-duration at intermediate ranges that was 

67 percent higher by 2020 than under the Air Force’s 

plan. Furthermore, the improved survivability of the 

MQ-SXs could make them more useful in environments 

posing a greater threat.

Option 3—Buy 24 MQ-SXs and 24 Fewer Global Hawks 

(Lower Cost). Starting in 2012, the Air Force would 

buy 24 fewer Global Hawks and the same number of 

MQ-SXs. Although the total number of aircraft purchased would be nearly the same as under the Air Force’s 

current plans, the total cost would decrease by about 

$3.7 billion. The overall payload-duration would be 

reduced at all ranges under Option 3 because the MQ-SX 

would be slower (and therefore take longer to reach the 

target area), have less endurance, and have a slightly lower 

payload than the Global Hawk. In addition, the sensors 

available with the MQ-SX might be less effective than 

those designed for the Global Hawk, but with further 

investment it might be possible to modify Global Hawk 

sensors for use on the MQ-SX. Although payload-duration would decrease, weapons payload would increase 

because the Global Hawk is not currently configured to 

carry weapons. Also, the stealth features of an MQ-SX 

might enable it to operate in defended airspace that 

would be too hazardous for a Global Hawk.

6. At least two aircraft that might meet those criteria are flying 

today—the General Atomics Avenger and the RQ-170 Sentinel. 

The two aircraft have significant differences: the Avenger 

resembles a Global Hawk with the addition of airframe shaping 

for stealth, whereas the Sentinel has a tailless design resembling 

the B-2 bomber. Aircraft at this stage of development could enter 

production more quickly than would be possible if starting from 

scratch.
SUMMARY POLICY OPTIONS FOR UNMANNED AIRCRAFT SYSTEMS XIII

CBO

Summary Figure 2.

Change in Capability at Different Ranges and in Acquisition Cost in 2020 

Under CBO’s Options for the Air Force

(Billions of 2011 dollars)

Source: Congressional Budget Office.

Notes: The overall approach of the options would be to buy new, stealthier aircraft, as follows:

• Option 1—Buy 224 MQ-SXs and 336 Fewer Reapers

• Option 2—Buy 336 MQ-SXs and 336 Fewer Reapers

• Option 3—Buy 24 MQ-SXs and 24 Fewer Global Hawks

The MQ-SX is a notional unmanned aircraft system based on existing aircraft systems that is more capable than the Predator class in 

speed and altitude and less capable than the Global Hawk class.

Capability is measured as payload-duration—a comparative performance metric developed by CBO. It measures the weight (payload) 

an unmanned aircraft could carry to a location, multiplied by the amount of time the aircraft could stay there on orbit (duration). The 

symbols in the figure represent that capability for the overall fleet in orbits at three distances from the airbase (275, 1,500, and 2,500 

nautical miles) for each option. 

The figure compares payload-duration at different ranges with cost, but each option has other advantages and disadvantages not 

reflected in the comparison. 

Acquisition cost includes the cost of procuring air vehicles, sensors, and ground stations, plus the cost for research, development, 

test, and evaluation. 

Options for the Army

CBO examined five options for the Army. Two (Options 

4 and 5) explore the implications of buying systems that 

are more capable than the ones the Army plans to buy. A 

third (Option 6) examines the effects of buying a greater 

quantity of less capable systems. Two others (Options 7 

and 8) illustrate the effects of changing the way that 

unmanned systems are assigned to military units and are 

operated in the theater of combat: Instead of being 

equipped with their own aircraft, deployed divisions 

would be given operational control of aircraft from a 

central fleet. That approach, called remote-split operations, is one the Air Force has used successfully with 

its unmanned aircraft. Options 7 and 8 would result in 

savings from buying fewer aircraft because of the 

remote-split technique. None of the five options consider 

systems or concepts that are in the early stages of development, such as the Long Endurance Multi-Intelligence 

Vehicle—an unmanned airship that the Army is currently 

investigating. 

  

Range (Nautical miles)

275 1,500 2,500

 





Less Capability,

Higher Cost

More Capability,

Higher Cost

More Capability,

Lower Cost

Less Capability,

Lower Cost

Option 3

Option 2

Option 1

Percentage Change in Capability in 2020

Compared with the Air Force's 2012 Plan

-100 -50 0 50 100 150

-5

-4

-3

-2

-1

0

1

2

3




XIV POLICY OPTIONS FOR UNMANNED AIRCRAFT SYSTEMS

CBO

Option 4—Buy 69 Reapers and 78 Fewer Grey Eagles 

(Same Cost). The Army would replace future purchases 

of 78 Grey Eagles with 69 larger, more costly Reaper aircraft to arrive at the same overall acquisition cost as its 

current plan. The Grey Eagles already purchased would 

remain in service. Because of its greater payload, range, 

and endurance, the Reaper would provide 53 percent to 

86 percent greater payload-duration by 2020 than the 

Grey Eagle (see Summary Figure 3). Although the Reaper 

costs more than the Grey Eagle, the difference in unit 

cost is less than one might expect, because the aircraft is 

only part of the system being purchased. Both systems 

require essentially the same ground stations and communications links. Another advantage of the Army’s buying 

Reapers rather than continuing to develop its own unique 

system is that doing so would increase commonality 

between the Air Force and Army systems. Commonality 

could reduce production costs because economies of scale 

affect the manufacturing process. CBO did not include 

any such savings in its calculations.

Option 5—Buy 78 Reapers and 78 Fewer Grey Eagles 

(Higher Cost). The Army would replace future purchases 

of 78 Grey Eagles with the same number of larger, more 

costly Reaper aircraft. The Grey Eagles already purchased 

would remain in service. CBO estimates that this option 

would provide 67 percent to 105 percent more payloadduration than the Army’s plan but would cost about 

$520 million more. 

Option 6—Buy 350 Firescouts and 78 Fewer Grey Eagles 

(Same Cost). The Army would purchase 350 MQ-8 

Firescout unmanned helicopters and 78 fewer Grey 

Eagles to arrive at the same overall acquisition cost as 

the 2012 plan. The Grey Eagles already purchased 

would remain in service. The range and payload of the 

Firescouts are much lower than those of the Grey Eagle, 

but because the Firescouts cost less, the Army could purchase more of them.7

 The resulting payload-duration of 

Option 6 would be 60 percent greater than that of the 

2012 plan at a range of 40 nm but would fall to about 

half that of the plan at 650 nm.

Option 7—Conduct Remote-Split Operations with 

42 Fewer Grey Eagles (Lower Cost). The Army would 

change the way it assigns and operates unmanned aircraft 

in combat theaters. It would centralize its force of 

medium-altitude unmanned aircraft systems in operations referred to as remote-split—an approach that has 

worked well for the Air Force in Iraq and Afghanistan. 

Deployed divisions would be given operational control of 

aircraft from a central fleet, instead of being equipped 

with their own aircraft. Although the aircraft would be 

under the control of the division commander, they could 

be operated over satellite links from the United States or 

other secure locations. 

In this option, the Army would buy 42 fewer Grey 

Eagles, saving $1.3 billion relative to the 2012 plan. 

A set of 113 Grey Eagles would provide support for up to 

six divisions on the ground—about the size of the peak 

U.S. deployment in Operation Iraqi Freedom—and three 

additional division sets would be available for special 

operations, training, or holding in reserve. Although the 

Army would have less overall payload-duration at all 

ranges compared with its 2012 plan, deployed units 

would have the same payload-duration as they would 

under that plan because the divisions would have the 

same number of aircraft supporting them, although those 

aircraft would be operated centrally in the geographic 

areas where units are deployed. 

Option 8—Conduct Remote-Split Operations with 

36 Reapers and 78 Fewer Grey Eagles (Lower Cost). 

The Army would adopt remote-split operations, as in 

Option 7, but would replace some of the Grey Eagles 

with Reapers: The same-size force of 113 mediumaltitude unmanned aircraft would consist of 77 Grey 

Eagles and 36 Reapers. As in Option 7, the fleet of 

unmanned aircraft would be able to support up to six 

divisions on the ground, and three additional division 

sets would be available for special operations, training, 

or holding in reserve. Under this option, deployed units 

would have 37 percent to 56 percent greater payloadduration at short and long ranges, respectively, than in 

Option 7 and the Army’s plan. This approach would cost 

$1.0 billion less than the Army’s plan.

7. The Class IV MQ-8 Firescout is a small helicopter and therefore 

does not require a runway from which to operate. Option 6 would 

replace the division-level Grey Eagle with the Firescout, which 

could be assigned to either a division or separate brigades. The 

Army has considered purchasing Firescout for its combat brigades 

but has not yet done so.
SUMMARY POLICY OPTIONS FOR UNMANNED AIRCRAFT SYSTEMS XV

CBO

Summary Figure 3.

Change in Capability at Different Ranges and in Acquisition Cost in 2020 

Under CBO’s Options for the Army

(Billions of 2011 dollars)

Source: Congressional Budget Office.

Notes: Under the options, the Army would buy more-capable aircraft (Options 4 and 5); buy more, less-expensive aircraft (Option 6); or 

change the way aircraft are operated (Options 7 and 8), as follows:

• Option 4—Buy 69 Reapers and 78 Fewer Grey Eagles

• Option 5—Buy 78 Reapers and 78 Fewer Grey Eagles

• Option 6—Buy 350 Firescouts and 78 Fewer Grey Eagles

• Option 7—Conduct Remote-Split Operations with 42 Fewer Grey Eagles

• Option 8—Conduct Remote-Split Operations with 36 Reapers and 78 Fewer Grey Eagles

Capability is measured as payload-duration—a comparative performance metric developed by CBO. It measures the weight (payload) 

an unmanned aircraft could carry to a location, multiplied by the amount of time the aircraft could stay there on orbit (duration). The 

symbols in the figure represent that capability for the overall fleet in orbits at two distances from the airbase (40 and 650 nautical 

miles) for each option. Options 7 and 8 show a further comparison of capability for deployed divisions, in case the Army decides to 

employ the remote-split technique (in which deployed divisions would have operational control of aircraft from a central fleet rather 

than be equipped with their own aircraft).

The figure compares payload-duration at different ranges with cost, but each option has other advantages and disadvantages not 

reflected in the comparison.

Acquisition cost includes the cost of procuring air vehicles, sensors, and ground stations, plus the cost for research, development, 

test, and evaluation.

n.a. = not applicable.







Option 7

Option 5

Option 6





Option 4

Percentage Change in Capability in 2020

Compared with the Army's 2012 Plan

Less Capability,

Higher Cost

More Capability,

Higher Cost

More Capability,

Lower Cost

Less Capability,

Lower Cost

Range

(Nautical miles) Overall Fleet Deployed Divisions

40

650

40 and 650





n.a. 

-100 -50 0 50 100 150

-5

-4

-3

-2

-1

0

1

2

3

Option 8



CHAPTER

CBO

1

Existing Unmanned Aircraft 

Systems and Future Plans

From 2011 to 2020, the Department of Defense 

(DoD) plans to buy 730 medium-sized and large 

unmanned aircraft systems that are designed for conducting reconnaissance missions or for attacking targets on 

the ground.1

 The Congressional Budget Office (CBO) 

estimates that acquiring those systems will cost about 

$36.9 billion over 10 years. 

All of the U.S. military services are actively considering a 

large increase over the long term in their inventories of 

unmanned aircraft systems and in the types of missions 

those systems would perform. In a 2009 Air Force publication, for example, missions for unmanned aircraft 

systems were envisioned to expand from today’s missions 

of reconnaissance and attacking ground targets to a much 

wider array of missions, including personnel recovery, airborne refueling, medical evacuation, and missile defense.2

Although conceptual plans for expanding unmanned 

aircraft systems over the long term are limited only by 

the availability of technology and the imagination of 

planners, near-term programs have been focused 

primarily on unmanned aircraft systems designed for 

reconnaissance missions and for light attack of targets on 

the ground.3

 That more limited focus is driven largely by 

the need to support counterinsurgency operations in Iraq 

and Afghanistan but also by the need to develop additional technologies to enable unmanned aircraft systems 

to perform more functions. Several aircraft—ranging in 

size from the Global Hawk, which has a wingspan of 

131 feet, to small systems that can be carried in backpacks—are being openly developed or purchased. In 

addition, the Air Force has acknowledged development 

work on some classified systems, including the RQ-170 

Sentinel, a stealthy unmanned aircraft system.4

This study analyzes the effects on capability and acquisition cost of eight alternatives to DoD’s near-term plans 

for expanding its fleet of medium-sized and large 

unmanned aircraft that are designed for reconnaissance 

and light attack missions. Those systems have been 

openly acknowledged by DoD and have been fielded or 

could be fielded in the near future. The aircraft differ in 

endurance, speed, altitude, payload, and cost. Because 

they are unmanned, they can undertake new missions 

and reduce the risks of traditional missions. Near-term 

acquisition plans for those medium-sized and large systems are sufficiently well defined to make it possible to 

estimate the capabilities that could be provided for different levels and types of investment. Those systems also 

represent the greater part of planned investments for 

unmanned aircraft in the near term. In contrast, longerterm plans are so general at this time as to be little more 

than a list of missions that such systems could be built to 

fly; those plans will require further refinement before a 

meaningful analysis of alternatives is possible.

1. This study uses the term “reconnaissance” generically to describe 

all intelligence, surveillance, and reconnaissance (ISR) missions. 

The military defines reconnaissance as an operation that uses 

assets to observe an area to collect information; it further defines 

surveillance as the systematic observation of a particular area. 

Once the information from those operations has been analyzed 

and evaluated, it is referred to as intelligence. 

2. U.S. Air Force, Headquarters, United States Air Force Unmanned 

Aircraft Systems Flight Plan 2009–2047 (May 18, 2009).

3. The term “light attack” is used here to denote the ability of today’s 

unmanned aircraft systems to carry small numbers of relatively 

light weapons. For example, the Reaper can carry two 500-pound 

(lb) guided bombs and four 100-lb Hellfire missiles. In contrast, 

the F-16 fighter jet can carry four 2,000-lb bombs or eight 500-lb 

bombs in some configurations, although it usually carries fewer 

weapons to increase its range.

4. Office of the Secretary of the Air Force, Directorate of Public 

Affairs, “RQ-170 Sentinel” (Air Force fact sheet, December 2, 

2010), www.af.mil/information/factsheets/factsheet

.asp?ID=16001.
2 POLICY OPTIONS FOR UNMANNED AIRCRAFT SYSTEMS

CBO

Figure 1-1.

Missions Performed by Unmanned Aircraft, by Altitude and Endurance 

Source: Congressional Budget Office. 

Note: The missions can usually be accomplished at all altitudes; the current unmanned aircraft perform the missions as shown.

a. The MQ-SX is a notional aircraft. The illustration shows the types of missions it could perform and the altitude at which it would operate 

but does not reflect an actual design.

b. Endurance is the maximum length of time an aircraft can spend in the air. 

Missions

The Congressional Budget Office’s (CBO’s) analysis 

focuses on capabilities of unmanned aircraft systems for 

reconnaissance and light attack missions, recognizing 

that those systems could also be used for many other 

missions. In reconnaissance missions, an aircraft uses its 

sensors to detect and observe objects on land or sea, or to 

intercept and analyze electronic emissions from ground, 

sea, or air sources. A properly designed medium-sized or 

large unmanned aircraft can perform a variety of 

reconnaissance missions. The aircraft vary by the altitudes 

at which they fly, but most missions can be accomplished 

at different altitudes. (However, some reconnaissance 

missions may require specific unmanned aircraft because 

of the aircraft’s size, operating characteristics, or sensors.) 

Therefore, CBO’s analysis can consider combinations of 

various types of aircraft to accomplish the same missions. 

The important variations are the length of time the aircraft can remain in the air (endurance, see Figure 1-1) 

and the amount of weight they can carry (payload). 

Reconnaissance missions can be combined with attack 

Endurance (Hours)b

12 24 36

Missions

Signal Intelligence

Communications Relay

(Tactical)

Armed Reconnaissance/

Attack

Jamming 

Full-Motion Video

Surveillance

Force Protection

Signal Intelligence 

Communications Relay 

(Theater)

Wide-Area Surveillance

Signal Intelligence

Communications Relay

(Theater)

Wide-Area Surveillance

Armed Reconnaissance/

Attack

0

Altitude

(Thousands

of feet)

Sea Level

15

30

45

60

*

*

MQ-SXa

RQ-7 Shadow

MQ-8 Firescout

MQ-5B Hunter

MQ-1 Predator

MQ-1C Grey Eagle

MQ-9 Reaper

RQ-4 Global Hawk/

Broad Area Maritime Surveillance
CHAPTER ONE POLICY OPTIONS FOR UNMANNED AIRCRAFT SYSTEMS 3

CBO

missions if the systems can carry weapons. Alternatively, 

if the primary objective of a mission is to destroy a particular target, the system may carry a full load of weapons, 

thus reducing its endurance and, perhaps, the number of 

sensors on board.

For many missions, the complications inherent in removing pilots from aircraft—in particular, the need for 

ground stations and the transmission of large amounts of 

data via satellite—are worth the effort. The advantages 

most commonly cited by proponents of unmanned aircraft fall into three categories:

 Enabling missions that would be constrained by the 

physiological limitations of a human crew (usually for 

long-endurance missions or for extreme maneuvers 

that subject the aircraft and pilot to accelerations 

many times the force of gravity),

 Saving pilots’ lives during dangerous missions or 

reducing the political risks that result when pilots are 

captured, and

 Lowering costs by eliminating the aircraft systems 

needed to support a pilot (such as oxygen, climate 

controls, and ejection seats) and by enabling the 

design to be less airworthy than if crews were on 

board.

Although removing pilots from aircraft can offer advantages in those areas, it also can introduce disadvantages. 

The appendix provides additional details on missions 

and further discussion of the reasons for using unmanned 

aircraft systems.

Existing Systems 

The types of unmanned aircraft in operation today in the 

U.S. military vary widely. Current systems are generally 

grouped into three categories based essentially on size:

 Large aircraft, which have the wingspan of a commercial airliner. They fly at high altitude (50,000 to 

60,000 feet) and have very long endurance (up to 

36 hours in the air).

 Medium-sized aircraft, which range in size from the 

single-engine Cessna up to fighter aircraft. They fly at 

medium altitude (30,000 to 45,000 feet) and can have 

long endurance (18 to 24 hours). 

 Small (or tactical) unmanned aircraft systems, which 

can be operated by small military units in the field. In 

many cases, they do not require runways but instead 

can be catapulted from vehicles or hand-launched by 

soldiers like remote-control hobby airplanes. They fly 

at low altitude (below 10,000 feet) and have short 

endurance (1 to 10 hours).

Although specific aircraft can be designed to emphasize 

particular attributes, larger aircraft tend to stay in the air 

for a longer time, fly at faster speeds, operate at higher 

altitudes, and support more-capable and heavier payloads 

of sensors and weapons. 

The Department of Defense currently has more than 

6,000 unmanned aircraft and is continuing to acquire 

more. The majority of those aircraft are short-range 

reconnaissance systems that have a wingspan of a few feet 

and have handheld controls used by small military units 

to look “around corners” or “over hills.” Less numerous, 

but more expensive, are the medium-sized and large 

unmanned aircraft systems fielded or in development for 

the Air Force, the Army, and the Navy and Marine Corps 

(see Table 1-1). 

Air Force Systems

The Air Force currently operates three types of mediumsized and large unmanned aircraft systems for which 

inventories and general performance characteristics are 

unclassified: the RQ-4 Global Hawk, the MQ-1 Predator, and the MQ-9 Reaper (referred to in this study as the 

Global Hawk, the Predator, and the Reaper).

The largest system is the turbofan-powered Global 

Hawk, and the Air Force has 14 of them in its inventory 

in 2011. The Global Hawk does not carry weapons: It is 

only a reconnaissance aircraft. The Global Hawks currently in operation carry optical and radar sensors for 

imaging objects on the ground and other sensors for 

detecting electronic emissions. Seven of the Global 

Hawks carry electro-optical and infrared sensors and a 

synthetic aperture radar; six carry an improved electrooptical and infrared sensor suite plus the synthetic 

aperture radar; and one will be retrofitted to also carry the 

Advanced Signals Intelligence Package for intercepting 

electronic transmissions. Plans also call for a later version 

of the Global Hawk to carry a more advanced synthetic 

aperture radar. 
4 POLICY OPTIONS FOR UNMANNED AIRCRAFT SYSTEMS

CBO

Table 1-1. 

Characteristics of Medium-Sized and Large Unmanned Aircraft Systems 

Fielded or Under Development

Source: Congressional Budget Office based on data from the Department of Defense.

Note: lb = pounds. 

a. Systems use aviation fuel unless otherwise specified.

b. The service ceiling is the maximum routine altitude at which an unmanned aircraft flies.

c. A knot is a unit of speed equal to one nautical mile per hour.

d. The MQ-SX is a notional unmanned aircraft system based on existing aircraft systems that is more capable than the Predator class in 

speed and altitude and less capable than the Global Hawk class.

e. Endurance values are for surveillance versus armed reconnaissance missions (surveillance/armed reconnaissance); those values are lower 

when aircraft carry weapons.

f. These aircraft use heavy fuel—a standard fuel also used in the Army’s ground vehicles.

g. Endurance is 5 hours with a 110-lb payload and 10 hours with a 45-lb payload.

Wingspan/ Service Transit Maximum 

Body Length Ceilingb Speed Airfield Endurance Payload 

Type of Aircraft Propulsiona (Feet) (Feet) (Knots)c Requirement (Hours) (Pounds) Armament

Air Force RQ-4A (Block 10) Turbofan 116/44 65,000 340 Paved 35 2,000 None

Global Hawk

Air Force RQ-4B (Blocks 20, Turbofan 131/48 60,000 320 Paved 36 3,000 None

30, 40) Global Hawk

Navy RQ-4 Broad Area Turbofan 131/48 60,000 320 Paved 30 3,200 (Internal); None

Maritime Surveillance 2,400 (External)

MQ-SXd Turbofan 65/45 50,000 270 Paved 18 2,750 Varies up to

one 2,000-lb

guided bomb

Air Force MQ-1B Predator Piston engine 55/27 25,000 100 Paved 24/20e 450 2 Hellfire missiles

Air Force MQ-9 Reaper Turboprop 66/36 30,000 190 Paved 21/17e 3,750 Varies up to

two 500-lb

guided bombs;

4 Hellfire missiles

Army MQ-1C Grey Eagle Piston enginef 56/28 29,000 150 Paved 26/15e 800 4 Hellfire missiles

Navy MQ-8 Firescout Turboshaft 28/30 20,000 125 None 5 600 Under development

(Army version, Class IV)

Army and Marine Corps RQ-7 Shadow Rotary enginef 14/11 20,000 110 Dirt or grass 5 60 None

Army RQ-7C Shadow Rotary enginef 20/11 18,000 110 Dirt or grass 5g 110 Under development

Army MQ-5B Hunter Two piston 34/23 18,000 110 Paved 18 280 None

engines

Large, High-Altitude Global Hawk Variants

Medium-Sized, Medium-Altitude Predator Variants

Other Medium-Sized, Medium-Altitude Systems
CHAPTER ONE POLICY OPTIONS FOR UNMANNED AIRCRAFT SYSTEMS 5

CBO

The most numerous system in the Air Force is the Predator. The 2011 force includes about 175 of that pistonengine propeller aircraft, which can take still or video 

imagery and shoot Hellfire missiles. A larger version of 

the Predator, the turboprop-powered Reaper, is beginning 

to enter the force, and about 40 have been delivered as of 

2011. The Reaper offers greater range and payload than 

the Predator. Because they carry weapons, Reapers can 

perform reconnaissance and light attack missions. By carrying fewer weapons, the aircraft can stay in the air longer 

or carry additional sensors. 

Army Systems

The Army currently operates three medium-sized 

unmanned aircraft systems: the RQ-7 Shadow and the 

MQ-5B Hunter (referred to in this study as the Shadow 

and the Hunter) and a small number of Predator variants. 

Hunters were first fielded in the 1990s as reconnaissance 

aircraft that carried infrared and visible spectrum cameras. Some were later converted to carry the small 

GBU-44 precision attack weapon. About 20 Hunters 

remain in the inventory, but the Army plans to retire 

them by 2013. 

The most numerous system in the Army’s inventory is the 

Shadow. A smaller aircraft with a 60-pound payload, the 

Shadow carries infrared and visible spectrum cameras for 

day- and nighttime reconnaissance. In 2009, the Army 

completed purchases of 115 Shadow systems, each having 

four aircraft. Those aircraft are primarily operated at the 

brigade level (the echelon below division) within the 

Army’s force structure because their shorter range is 

suited to the limited operating area of a brigade. As of 

2011, the Army is upgrading its Shadows with improved 

communications systems and laser designators for guiding weapons fired by other platforms, such as artillery. 

The Shadow does not carry its own weapons, but the 

Army is working on developing that capability.

The Army purchased about 50 Predator class unmanned 

aircraft systems from 2004 through 2010 in three different versions called Warrior Alpha, MQ-1C Grey Eagle 

Block 0, and MQ-1C Grey Eagle. The first two aircraft 

are early, less capable preproduction versions of the Grey 

Eagle. The Army intends to operate those aircraft at the 

division echelon because they have the necessary range 

to cover the larger area typically assigned to a division 

(compared with that assigned to a brigade). In counterinsurgency operations like those in Iraq and Afghanistan, 

the distinction between echelons blurs because military 

units operate in small groups that can be widely scattered. 

Even a Grey Eagle might at times support a small unit in 

contact with an enemy.

Navy and Marine Corps Systems

The Navy is currently testing two new types of aircraft it 

hopes to field in the near future: the MQ-8 Firescout 

unmanned helicopter (referred to in this study as the 

Firescout), and the long-endurance Broad Area Maritime 

Surveillance (BAMS) aircraft, a variant of the Global 

Hawk modified to suit maritime operations. Although 

test versions of Firescout and BAMS aircraft have been 

delivered to the Navy, they have not officially entered 

operational service as of 2011.

The Marine Corps fielded the Shadow to support 

ongoing operations in Southwest Asia. Thirteen systems 

(with four aircraft per system) had been delivered by the 

end of calendar year 2009. 

Future Plans

In DoD’s 2012 budget request, acquisition funding for 

research, development, test, and evaluation and for procurement of currently planned medium-sized and large 

unmanned aircraft systems totals about $4.6 billion for 

2012. That total captures about 90 percent of DoD’s 

request of $5.1 billion for all unmanned aircraft systems 

in 2012 (see Figure 1-2).

Under DoD’s budget, funding for currently planned 

medium-sized and large systems would range between 

$3.7 billion and $5.7 billion annually over the next five 

years and would tend to decrease over time (except for a 

small increase in 2017), falling to just $2.4 billion by 

2020. That profile reflects DoD’s goal to acquire and 

deploy existing types of unmanned aircraft systems as 

quickly as possible to support ongoing counterinsurgency 

operations. DoD’s total requested funding for unmanned 

aircraft systems probably will not fall if new programs 

to develop more advanced aircraft come into being in 

later years.

To facilitate comparisons of the capability of various 

systems, CBO constructed a measure called payloadduration—defined as the weight (payload) that an 

unmanned aircraft could carry to a location, multiplied 

by the amount of time the aircraft could stay there on 

orbit (duration). The systems were analyzed according 

to the payload-duration they could provide for orbits 

positioned at various distances from the airbase from 

which they would operate. (See Box 1-1 on page 8 for 

more detail about payload-duration.) 
6 POLICY OPTIONS FOR UNMANNED AIRCRAFT SYSTEMS

CBO

Figure 1-2.

Acquisition Cost of Medium-Sized and Large Unmanned Aircraft Systems and of 

All Systems Under the Department of Defense’s 2012 Plan

(Billions of 2011 dollars)

Source: Congressional Budget Office based on data from the Department of Defense’s budget request for 2012, Selected Acquisition

Reports for December 2010, and Aircraft Procurement Plan: Fiscal Years 2012–2041 (submitted with the 2012 budget, 

March 2011).

Notes: Acquisition cost is the cost of procuring air vehicles, sensors, and ground stations, plus the cost for research, development, test, and 

evaluation. The services’ cost data have been adjusted using CBO’s projection of inflation.

DoD did not report, nor did CBO estimate, the acquisition cost of all systems beyond 2015.

Air Force’s Plans

The Air Force’s near-term goals are to increase the 

number of Global Hawk and Reaper aircraft that can be 

continuously and simultaneously operated. To meet that 

goal, the Air Force plans to purchase 288 Reapers (48 per 

year from 2011 through 2016) and 28 Global Hawks 

from 2011 through 2018. Documents that DoD provided to the Congress with its 2012 budget request indicate plans to continue buying multimission unmanned 

aircraft after 2016, although the type of aircraft is not 

specified.5

 On the basis of the information available, 

CBO assumed that the Air Force’s purchases after 2016 

would continue at 48 aircraft per year and would comprise either additional Reapers or a follow-on aircraft 

with range, payload, and cost similar to the Reaper. 

(Unless a distinction is necessary, references to the 

Reaper in this study pertain to both the Reaper itself 

and the possible follow-on system.)

About $20.4 billion will be needed to purchase those 

aircraft, CBO estimates: $7.3 billion for Global Hawks, 

$13.1 billion for Reapers, and about $60 million to 

complete production of Predators (see Table 1-2). 

Those costs would average about $2.0 billion per year 

through 2020.

Of the 38 Global Hawks purchased through 2010, 14 are 

operational. The remaining aircraft have not yet been 

delivered or are waiting for their sensors to be tested. 

Under its 2012 plan, the Air Force will have purchased a 

total of 66 Global Hawks by 2018, although CBO estimates that about 7 of those aircraft could be lost to 

attrition from accidents or enemy action by then.6

 When 

the planned Global Hawks are fully operational, the Air 

Force expects to retire its remaining U-2S manned reconnaissance aircraft, although some or all of those aircraft 

may remain in service if needed to augment Global 

Hawks or any other high-altitude reconnaissance systems 

that might be deployed by that time.7

2011 2012 2013 2014 2015 2016 2017 2018 2019 2020

0

1

2

3

4

5

6

7

All Systems

Medium-Sized and Large Systems

5. Department of Defense, Aircraft Procurement Plan: Fiscal Years 

2012–2041 (submitted with the 2012 budget, March 2011). 

CBO adjusted the costs using its projection of inflation.

6. DoD does not publish an estimate of attrition losses. CBO used 

attrition rates based on historical values provided by the Air Force 

and the Army.

7. The U-2S carries some sensors not currently planned for the 

Global Hawk, and some missions may need a pilot on board.
CHAPTER ONE POLICY OPTIONS FOR UNMANNED AIRCRAFT SYSTEMS 7

CBO

Table 1-2. 

Quantity and Cost of Acquisitions Under the Air Force’s 2012 Plan

Source: Congressional Budget Office based on data from the Department of Defense’s budget request for 2012, Selected Acquisition

Reports for December 2010, and Aircraft Procurement Plan: Fiscal Years 2012–2041 (submitted with the 2012 budget, 

March 2011). 

a. Data are for the follow-on aircraft the Air Force plans to acquire instead of the Reaper.

b. Acquisition cost includes the cost of procuring air vehicles, sensors, and ground stations, plus the cost for research, development, test, 

and evaluation. The Air Force’s cost data have been adjusted using CBO’s projection of inflation and rounded to the nearest $10 million.

c. The Air Force has no plans to acquire or modify the specified system in these years.

At the beginning of 2010, Predators were the Air Force’s 

predominant medium-sized unmanned aircraft for 

reconnaissance and light attack missions. The Air Force 

estimates that its fleet of unmanned aircraft will be able 

to fly 50 continuous orbits by the end of 2011 and 

65 orbits by 2013 and that the more-capable Reaper will 

account for an increasing fraction of those orbits over 

time.8

 (The last of the Predators were purchased in the 

2009 budget, but some small modifications are still 

planned.) 

The Air Force plans to stop buying Reapers in 2016 and, 

in 2017, to start purchasing a follow-on medium-sized 

unmanned aircraft system. Although the Air Force has 

not yet identified what the follow-on aircraft will be, in 

estimating payload, endurance, and cost CBO has 

assumed that the aircraft will be similar to the Reaper; 

accordingly, discussions about the Reaper in this study 

also apply to the follow-on aircraft, unless making the 

distinction is necessary. (For example, a follow-on to the 

Reaper is likely to have improved stealth characteristics.) 

In 2020, the Air Force’s inventory (incorporating losses 

due to attrition) would include about 600 Predators and 

Reapers that would be capable of sustaining more than 

100 continuous orbits, CBO estimates (see Figure 1-3 on 

page 10).9

In addition to a larger number of aircraft and the 

corresponding increase in the number of orbits, the effectiveness of the aircraft on orbit will increase, on average, 

because the aircraft to be added under the Air Force’s plan 

will be more capable than most of the aircraft in the force 

today. The extent to which the improved performance 

will make military operations more effective will depend 

on the types of missions and targets that present themselves in the future. 

The later-version Global Hawks have a 50 percent larger 

payload capacity than the original model and are slated to 

carry improved electro-optical and infrared sensors. Some 

will also carry sophisticated signals intelligence sensors or 

significantly improved synthetic aperture radar being 

developed by the Multi-Platform Radar Technology 

Total,

2011-

2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2020

RQ-4 Global Hawk 4 3 3 3 1 1 6 7 0 0 28

MQ-1 Predator 0 0 0 0 0 0 0 0 0 0 0

MQ-9 Reaper 48 48 48 48 48 48 48 a 48 a 48 a 48 a 480 a

___ ___ ___ ___ ___ ___ ___ ___ __ __ ____

Total 52 51 51 51 49 49 54 55 48 48 508

RQ-4 Global Hawk 1,200 1,060 890 790 810 710 1,160 530 80 60 7,290

MQ-1 Predator 30 10 10 10 c c c c c c 60

MQ-9 Reaper 1,700 1,550 1,740 1,440 1,350 1,150 1,060 a 1,040 a 1,030 a 1,010 a 13,070 a

_____ _____ _____ _____ _____ _____ _____ _____ ____ ____ ______

Total 2,930 2,620 2,640 2,240 2,160 1,860 2,220 1,570 1,110 1,070 20,420

Quantity

Cost (Millions of 2011 dollars)b

8. The Air Force uses a planning factor of four aircraft per continuous orbit, so 50 such orbits would require 200 aircraft.

9. Using historical data and the Air Force’s projections, CBO estimates that about 81 Predators and 52 Reapers will be lost through 

accidents or retirement by 2020.
8 POLICY OPTIONS FOR UNMANNED AIRCRAFT SYSTEMS

CBO

Continued

Insertion Program. At the same time, the Air Force’s 

future medium-altitude fleet will make the transition 

from one dominated by Predators to one dominated by 

Reapers, which fly at higher speeds and carry heavier 

payloads. The increased payload capacity can be used to 

carry more weapons or new sensors, such as the Gorgon 

Stare video sensor, which can look in several directions 

at once.

As a generalized measure of the projected increases in 

capabilities from the Air Force’s plans, CBO estimated 

payload-duration at three ranges from airbases to target 

areas. Typically, the ranges from airbases in a theater of 

deployment are zero to 650 nautical miles (nm), compared with 1,500 nm for airbases in a geographic region 

of deployment and 2,500 nm for airbases outside that 

region.10 By 2020, CBO estimates, the increase in 

Box 1-1.

Payload-Duration as a Comparative Measure of Capability

To facilitate comparison of the capability that can be 

expected under various plans for acquiring 

unmanned aircraft, the Congressional Budget Office 

(CBO) constructed a measure called payloadduration—that is, the weight (payload) that an 

aircraft could carry to a mission’s location (orbit), 

multiplied by the amount of time the aircraft could 

stay there on orbit (duration). Duration equals 

endurance (the maximum length of time that an 

aircraft can spend in the air) minus time in the transit 

phase, where total transit time is two times the range 

divided by transit speed (see the figure on the 

opposite page).

Payload-duration does not capture all aspects of 

performance that are relevant. However, it is a very 

useful measure for comparing the performance of two 

or more fleets under various options for the fleet’s 

composition.

For orbits positioned at various distances from 

the airbase from which the systems operate, CBO 

calculated the payload-duration that each alternative 

fleet of unmanned aircraft systems for each service 

could provide—that is, the sum of the payloadduration for each aircraft in that fleet.1

 In those 

calculations, transit time depends on the distance to 

the target area and the speed of the aircraft. Faster 

aircraft reach the target area more quickly and can 

spend more of their endurance time in the orbit 

phase. In cases in which an aircraft can carry different 

payloads with varying endurance, as the Reaper and 

the Grey Eagle can, CBO used a distribution of 

payload weights and associated endurance based 

on planning factors provided by each of the armed 

services. 

Fleetwide payload-duration captures the benefits of 

inventory, transit speed, endurance, and payload 

capacity. Payload capacity serves as a simplified measure of the types and quality of sensors and weapons 

that could be carried—under the general assumption 

that, all else being equal, a greater payload capacity 

offers the opportunity to carry more-capable sensors 

and a greater number or variety of weapons. For 

simplicity, the payload-duration metric counts all 

pounds of payload—sensors or weapons carried internally or on external racks—equally. Although the 

components of payload are to some extent interchangeable, current aircraft are limited to carrying 

specific sensors, weapons, or both. Nevertheless, the 

aggregate metric provides a useful measure of capacity 

for the overall fleet.

In the future, in-flight refueling could increase 

payload-duration at all ranges, and the Department 

of Defense is exploring technologies for automated 

aerial refueling. However, none of the aircraft systems 

considered in this study can be refueled in flight.

1. CBO’s estimates of payload-duration are based on total 

aircraft inventory for each service. In actuality, some fraction 

of each fleet will be unavailable for operations at any given 

time because of maintenance or upgrades. However, because 

the fraction of aircraft unavailable is likely to be similar across 

the options, payload-duration is a suitable measure for 

comparing the fleets’ capabilities.

10. A distance of 650 nm would probably be at the high end for 

airbases in a theater of operations. Closer airbases could be 

available, and commanders might prefer to base aircraft with 

shorter endurance at those locations. 
CHAPTER ONE POLICY OPTIONS FOR UNMANNED AIRCRAFT SYSTEMS 9

CBO

payload capacity for the Air Force fleet would be substantial, and the largest effects would be at ranges between 

275 and 650 nm, where Reapers and Global Hawks 

can remain in continuous orbits for long durations (see

Figure 1-4 on page 11).

The Army’s Plans

The largest programs for unmanned aircraft systems 

in the Army’s 2012 budget request are the purchase of 

107 Grey Eagle medium-altitude aircraft and 20 Shadows 

as well as upgrades to the existing fleet through 2016 (see 

Table 1-3 on page 12).11 CBO estimates that completing 

those programs would cost about $5.9 billion—$4.0 billion for the Grey Eagle and $1.9 billion for Shadow 

upgrades. Those costs would average $1.0 billion per year 

over the 2011–2016 period. The Army has a long-term 

plan for a follow-on medium-sized system starting in 

about 2026.

The Army plans to buy 20 additional Shadows to replace 

losses and also intends to upgrade its existing Shadows 

with a laser target designator and a new tactical communications data link for both the aircraft and the ground 

station. The upgrade of the laser target designator began 

in 2008, and the data link modernization began in 2010. 

The Army plans to upgrade the entire Shadow fleet.12

The Grey Eagle is a version of the Predator with a slightly 

more powerful engine and slightly larger payload. The 

Army plans to equip up to 10 combat aviation brigades 

with Grey Eagle systems, and the remaining aircraft 

will support special operations and undertake other 

missions.13

The Army has roughly 490 medium-sized unmanned aircraft in its inventory in 2011 (see Figure 1-3 on page 10). 

Box 1-1. Continued

Payload-Duration as a Comparative Measure of Capability

Phases of Flight for Unmanned Aircraft

Source: Congressional Budget Office.

Airbase

Transit Phase Orbit Phase

Target Area

Range

11. That total does not include the Grey Eagle aircraft the Army purchased before 2011, but it does include three purchased with 

funding for overseas contingency operations in 2011 to replace 

aircraft lost through attrition.

12. The Army may also upgrade the Shadow’s wings to increase its 

payload, but that decision has not yet been made.

13. A combat aviation brigade is part of an Army division; thus, it 

reports directly to an Army division commander when a division 

deploys as a unit.
10 POLICY OPTIONS FOR UNMANNED AIRCRAFT SYSTEMS

CBO

Figure 1-3.

Inventory of Medium-Sized and Large Unmanned Aircraft Under the 

Department of Defense’s 2012 Plan 

(Number of aircraft)

Source: Congressional Budget Office.

2011 2012 2013 2014 2015 2016 2017 2018 2019 2020

0

100

200

300

400

500

600

700

Predator

Reaper

Global Hawk

2011 2012 2013 2014 2015 2016 2017 2018 2019 2020

0

100

200

300

400

500

600

700

Shadow

Hunter

Grey Eagle

2011 2012 2013 2014 2015 2016 2017 2018 2019 2020

0

100

200

300

400

500

600

700

Shadow Firescout

Broad Area

Maritime Surveillance

Air Force

Army

Navy and Marine Corps
CHAPTER ONE POLICY OPTIONS FOR UNMANNED AIRCRAFT SYSTEMS 11

CBO

Figure 1-4.

Payload-Duration at Various Ranges Under the Air Force’s 2012 Plan

(Millions of pound-hours)

Source: Congressional Budget Office.

Notes: The ranges, expressed in nautical miles (nm), measure the distance from the aircraft’s airbase to orbit. All but the shortest range 

(275 nm) correspond to the maximum distances the Predator (650 nm), Reaper (1,500 nm), and Global Hawk (2,500 nm) can operate 

from their airbase.

Payload-duration is a comparative performance metric developed by CBO to measure overall capability. It measures the weight 

(payload) an unmanned aircraft could carry to a location, multiplied by the amount of time the aircraft could stay there on 

orbit (duration).

The inventory will remain roughly constant over the next 

four years as deliveries of Grey Eagles compensate for estimated attrition losses and the retirement of Hunters.14

CBO estimates that unless the Army buys additional aircraft, attrition will reduce the inventory of Shadows and 

Grey Eagles to about 400 aircraft by 2020.15

Except for the Grey Eagle, which has a satellite relay 

for longer ranges, the effective range of the Army’s 

unmanned aircraft systems, as currently equipped, is the 

line-of-sight communications range between the aircraft 

and their ground station. That line-of-sight range 

depends on the altitude at which the aircraft are able to 

fly; higher altitudes offer longer line-of-sight distances to 

ground stations to overcome terrain features and the 

curvature of the Earth. By contrast, the Air Force’s 

unmanned aircraft systems are not subject to that constraint because all are equipped with the satellite communications needed for theaterwide and global operations.

Although inventory would remain nearly constant over 

the next several years under the Army’s current plans, 

payload-duration would increase substantially as more 

Grey Eagles entered the force (see Figure 1-5 on page 13). 

Although the much greater endurance and payload of the 

Grey Eagle make it the dominant system in the future 

from a payload-duration perspective, the much larger 

inventory of Shadows enables a greater dispersion of sensors across the battlefield. Roughly speaking, the performance of each Grey Eagle offers missions of longer 

endurance over broader areas, whereas the large inventory 

of Shadows offers the ability to fly large numbers of more 

geographically constrained missions carrying a smaller 

payload. For example, the Shadow might perform a tactical mission with a limited scope, such as inspecting a 

route for obstacles or enemy forces before a ground unit 

2011 2012 2013 2014 2015 2016 2017 2018 2019 2020

0

2

4

6

8

10

12

14

16

18

20

275 nm

650 nm

1,500 nm

2,500 nm

14. On the basis of the Army’s data on losses, CBO assumed a 

constant rate of 5 percent attrition per year for Army systems. 

15. The Class IV unmanned aircraft system, an Army version of the 

Firescout helicopter, had been slated to provide a reconnaissance 

or light attack capability to combat brigades beginning about 

2015, but the Army canceled it along with the Future Combat 

System program in 2009.
12 POLICY OPTIONS FOR UNMANNED AIRCRAFT SYSTEMS

CBO

Table 1-3. 

Quantity and Cost of Acquisitions Under the Army’s 2012 Plan

Source: Congressional Budget Office based on data from the Department of Defense’s budget request for 2012, Selected Acquisition

Reports for December 2010, and Aircraft Procurement Plan: Fiscal Years 2012–2041 (submitted with the 2012 budget, 

March 2011).

a. From 2011 to 2015, the Army plans to upgrade existing RQ-7 Shadows and purchase 20 aircraft to replace combat losses.

b. Acquisition cost includes the cost of procuring air vehicles, sensors, and ground stations, plus the cost for research, development, test, 

and evaluation. The Army’s cost data have been adjusted using CBO’s projection of inflation and rounded to the nearest $10 million.

c. The Army has no plans to acquire or modify the specified system in these years.

moves, whereas the Grey Eagle might perform a continuous surveillance mission of a high-value target that might 

move over a large area.16 In addition, the Grey Eagle can 

include weapons in its payload, whereas the Shadow currently cannot. The Army is developing small air-toground weapons to be carried on modified Shadows. The 

cost of that modification is not included in this study.

Navy and Marine Corps’ Plans

The Navy plans to purchase about 68 unmanned aircraft 

as part of the Broad Area Maritime Surveillance program 

and would purchase 36 of that total by 2020 (see 

Table 1-4 on page 13 and Figure on page 10). The 

BAMS aircraft will be a version of the Global Hawk 

modified for maritime patrol. Although two test aircraft 

have undergone service test and evaluation, full production will not begin until 2015. Operating from just a few 

airbases worldwide, those aircraft will be used to maintain 

a general awareness of activities on the oceans.

The Marine Corps does not plan to purchase additional 

Shadow systems and instead will upgrade some existing 

systems. In the longer term, the Marine Corps is exploring concepts for a medium-sized system—notionally 

called the Group 4 UAS—that would be designed to 

perform various missions in support of amphibious 

operations.

To support the operations of surface ships, the Navy 

plans to purchase about 61 Firescout unmanned helicopters by 2020 (in addition to the 14 purchased before 

2011). The Firescout will operate from selected surface 

ships—especially the new littoral combat ships—to provide local reconnaissance and antiship capability.17 The 

Navy is testing several Firescouts for their suitability on 

ships, but the aircraft has not yet entered the fleet. The 

Navy will have a modest payload-duration until 2016, 

when deliveries of BAMS and Firescouts begin to increase 

(see Figure 1-6 on page 14). The Navy is also exploring 

concepts for a carrier-based unmanned aircraft, including 

the so-called Unmanned, Carrier-Launched Airborne 

Surveillance and Strike aircraft, that might enter service 

by 2020.

Total,

2011-

2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2020

MQ-1C Grey Eagle 29 36 28 14 0 0 0 0 0 0 107

RQ-7 Shadowa 0 20 0 0 0 0 0 0 0 0 20 ___ ___ ___ ___ ___ __ __ __ __ __ ____

Total 29 56 28 14 0 0 0 0 0 0 127

MQ-1C Grey Eagle 870 1,060 1,040 740 220 90 c c c c 4,020

RQ-7 Shadowa 610 250 270 200 300 280 c c c c 1,910 _____ ____ ____ ____ ____ ____ _____

Total 1,480 1,310 1,320 940 520 370 c c c c 5,940

Quantity

Cost (Millions of 2011 dollars)b

16. A Grey Eagle could perform the limited mission too if it did not 

have another task with a higher priority, whereas a Shadow would 

not be capable of the longer range and greater endurance of some 

of a Grey Eagle’s missions.

17. The littoral combat ship is a new class of Navy warship that is 

small, fast, and easier to maneuver than larger ships. For more 

information, see Congressional Budget Office, letter to the 

Honorable John McCain about analyzing the cost implications 

of the Navy’s plans for acquiring littoral combat ships

(December 10, 2010).
CHAPTER ONE POLICY OPTIONS FOR UNMANNED AIRCRAFT SYSTEMS 13

CBO

Figure 1-5.

Payload-Duration at Various Ranges Under the Army’s 2012 Plan

(Millions of pound-hours)

Source: Congressional Budget Office.

Notes: The ranges, expressed in nautical miles (nm), measure the distance from the aircraft’s airbase to orbit. The ranges correspond to the 

maximum distances the Firescout (40 nm), Shadow (68 nm), and Grey Eagle (275 nm, or 650 nm with satellite relay) can operate from 

their airbase.

Payload-duration is a comparative performance metric developed by CBO to measure overall capability. It measures the weight 

(payload) an unmanned aircraft could carry to a location, multiplied by the amount of time the aircraft could stay there on 

orbit (duration).

Table 1-4. 

Quantity and Cost of Acquisitions Under the Navy and Marine Corps’ 2012 Plan

Source: Congressional Budget Office based on data from the Department of Defense’s budget request for 2012, Selected Acquisition

Reports for December 2010, and Aircraft Procurement Plan: Fiscal Years 2012–2041 (submitted with the 2012 budget, 

March 2011).

Note: BAMS = Broad Area Maritime Surveillance.

a. From 2011 to 2014, the Navy and Marine Corps plan to upgrade existing RQ-7 Shadows, resulting in no additional aircraft but involving an 

acquisition cost.

b. Acquisition cost includes the cost of procuring air vehicles, sensors, and ground stations, plus the cost for research, development, test, 

and evaluation. The Navy and Marine Corps’ cost data have been adjusted using CBO’s projection of inflation and rounded to the nearest 

$10 million.

c. The Navy and Marine Corps have no plans to acquire or modify the specified system in these years.

2011 2012 2013 2014 2015 2016 2017 2018 2019 2020

0

0.2

0.4

0.6

0.8

1.0

1.2

40 nm

68 nm

275 nm

650 nm

Total,

2011-

2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2020

MQ-8 Firescout 3 3 3 5 5 6 6 10 10 10 61

RQ-4 BAMS 0 0 0 4 4 5 5 6 6 6 36

RQ-7 Shadowa 00000000000 __ __ __ ___ ___ ___ ___ ___ ___ ___ ____

Total 3 3 3 9 9 11 11 16 16 16 97

RQ-4 BAMS 530 560 760 880 900 1,010 1,230 1,260 1,130 1,130 9,390

MQ-8 Firescout 60 70 60 80 80 90 130 160 150 150 1,030

RQ-7 Shadowa 90 10 10 10 c c c c c c 120 ____ ____ ____ ____ ____ _____ _____ _____ _____ _____ ______

Total 680 640 830 970 980 1,100 1,360 1,420 1,280 1,280 10,540

Quantity

Cost (Millions of 2011 dollars)b
14 POLICY OPTIONS FOR UNMANNED AIRCRAFT SYSTEMS

CBO

Figure 1-6.

Payload-Duration at Various Ranges Under the Navy and Marine Corps’ 

2012 Plan 

(Millions of pound-hours)

Source: Congressional Budget Office.

Notes: The ranges, expressed in nautical miles (nm), measure the distance from the aircraft’s airbase to orbit. The range of 40 nm 

corresponds to the maximum distance the Firescout can operate from its airbase. The longer ranges (100 nm and 650 nm) 

represent the distances the Broad Area Maritime Surveillance system might cover. 

Payload-duration is a comparative performance metric developed by CBO to measure overall capability. It measures the weight 

(payload) an unmanned aircraft could carry to a location, multiplied by the amount of time the aircraft could stay there on 

orbit (duration).

2011 2012 2013 2014 2015 2016 2017 2018 2019 2020

0

0.5

1.0

1.5

2.0

2.5

40 nm

100 nm

650 nm
CHAPTER

CBO

2

Assessing Policy Options

Ihn addition to its analysis of the Department of 

Defense’s 2012 plans for procuring unmanned aircraft 

systems, the Congressional Budget Office examined how 

alternatives to those plans might affect the capability of 

the armed forces and the budgetary cost. In the past 

several years, plans for fielding unmanned aircraft systems 

have changed more substantially from year to year 

than has been typical for other types of weapon systems. 

That variability results from several factors, including:

 A reevaluation of priorities in DoD’s February 2010 

Quadrennial Defense Review Report, 

 A tension between designing systems tailored for 

counterinsurgency and systems tailored for conventional force-on-force military operations (a tension 

that is exacerbated by DoD’s having to develop and 

refine how it operates unmanned aircraft systems in 

the midst of existing conflicts), and

 Questions about which performance characteristics 

are preferable and how much capability is appropriate 

(questions that are more difficult to answer in the case 

of unmanned aircraft systems because those systems 

largely represent a new capability, not the replacement 

and improvement of a previously established capability that is already familiar to planners and operators).

The options CBO examined—three for the Air Force and 

five for the Army—involve changes in acquisition plans 

that could be made in the near term to shift the mix of 

capabilities in the force over the next decade.1

 The analysis explores the trade-offs between added (or reduced) 

capability and cost among the options relative to DoD’s 

2012 plan. In addition, this study does not assess the 

operation and support costs of the options. In CBO’s 

estimation, those costs would change little under the 

eight options because some of the options would require 

only modest changes in the number of personnel—a 

major contributor to those costs—and because differences in fuel consumption and the cost of spare parts 

probably would be minimal.2

The options in this study are meant to illustrate the 

comparative cost and capabilities created by different 

approaches over the next 10 years and are not designed to 

reach any specific goals or counter any specific adversaries 

that might arise in the future. CBO did not examine 

longer-term options for unmanned aircraft systems that 

would require significant technological developments, 

because what could be fielded and what might be needed 

remain too speculative for a detailed analysis.3

1. CBO did not examine any alternatives for the Navy and Marine 

Corps because they will have relatively few unmanned aircraft 

systems in the near term and because CBO wanted to keep the 

number of options to a manageable level. 

2. Some options would require modest changes in the number of 

personnel. Option 6 for the Army, for example, would increase 

the number of unmanned aircraft operators, but CBO assumed 

that the Army would provide those people from existing ranks, as 

it has done when adopting other unmanned aircraft systems. Conversely, Options 7 and 8 would require fewer personnel, but those 

savings are not included in CBO’s analysis. 

3. For example, the Army planned several types of unmanned aircraft systems as part of the Future Combat System program. The 

Army canceled that program in 2009 but is still considering how 

to integrate its innovative technologies into new systems. The 

Navy is moving toward integrating long-range unmanned aircraft 

systems into its maritime patrol force, is planning to operate 

unmanned helicopters from the deck of many ships in the fleet, 

and is developing the X-47B unmanned carrier aircraft demonstrator, a possible candidate for the Unmanned Carrier Launched 

Airborne Surveillance and Strike System. The Marine Corps is 

exploring the use of unmanned helicopters for resupplying its 

expeditionary forces and plans to have those aircraft support its 

units in Afghanistan.
16 POLICY OPTIONS FOR UNMANNED AIRCRAFT SYSTEMS

CBO

Options for the Air Force

The Air Force’s procurement plans outlined in DoD’s 

30-year aviation plan focus on expanding the fleets of 

Global Hawks for long-range reconnaissance and Reapers 

for multimission reconnaissance and light attack.4

 (Citing 

uncertainties about future threats and the rapid evolution 

of aircraft technologies, DoD’s 30-year aviation plan 

offers firm programmatic details only through 2016 and 

more general objectives only through 2020.) The nearterm focus on the proven Reaper is consistent with efforts 

to expand as rapidly as possible the capabilities that are in 

demand in current conflicts. In the future, however, other 

characteristics (particularly the ability to operate in 

defended airspace) may become more important and may 

be reflected in the follow-on aircraft planned after 2016. 

CBO’s options for the Air Force look at the implications 

of a more rapid development and fielding of unmanned 

aircraft systems that have characteristics that could be 

advantageous in a conflict against a more technologically 

capable adversary. The Air Force is exploring concepts 

and requirements for such an aircraft—commonly 

referred to as the MQ-X in discussions of future plans—

and aerospace companies, anticipating the Air Force’s 

interest, have made varying levels of investment in developing the next generation of multimission unmanned 

aircraft systems. For example, General Atomics Aircraft 

Company (the manufacturer of Predator, Reaper, and 

Grey Eagle) has built a flying prototype of the Avenger, 

an aircraft aimed at filling that role. Lockheed Martin has 

developed the stealthy RQ-170 Sentinel, which has been 

flying and could also fill that role, but details about that 

aircraft are classified.

In CBO’s options, the Air Force would purchase a 

notional “MQ-SX”—an aircraft that would have some 

characteristics similar to those under consideration for 

the proposed MQ-X—in lieu of some of the Reapers 

or Global Hawks in current plans. The MQ-SX postulated by CBO would be a jet-powered (turbofan) aircraft 

about one and a half times the size of the Reaper with an 

airframe designed to be more difficult for air-defense systems to detect and target. The larger size would enable 

the MQ-SX to carry a greater payload (sensors, weapons, 

or fuel); jet propulsion would allow the aircraft to reach 

its destination (a target or orbit location) in less time; and 

stealth features would improve its ability to operate in 

defended airspace. Less certain is how CBO’s notional 

MQ-SX would compare with the possible follow-on to 

the Reaper, purchases of which could begin in 2017 

according to DoD’s long-term aircraft procurement plan. 

For the purpose of calculating payload, endurance, and 

cost, CBO has assumed that the follow-on aircraft would 

be similar to the Reaper but would probably include 

improved stealth characteristics. CBO estimated the cost 

of the notional MQ-SX by scaling up the cost of the 

existing Reaper airframe to account for the change in size 

and for the addition of stealth features for improved survival in defended airspace. CBO’s cost estimate for the 

notional MQ-SX assumes modest efforts to improve 

stealth characteristics relative to the Global Hawk, Predator, and Reaper. A highly stealthy design would probably 

cost more. Ancillary equipment that can contribute substantially to the cost of unmanned aircraft systems (for 

example, ground stations and communications systems) 

is assumed to be similar to that of the Reaper. At least two 

aircraft that might meet those criteria are flying today 

(the Avenger and the RQ-170 Sentinel). All three options 

for the Air Force assume that an aircraft at a similar 

stage of development would be adopted and could enter 

production quickly with little funding for research and 

development beyond that already planned. 

A larger aircraft is able to carry various combinations of 

larger sensors, heavier weapon loads, or additional fuel for 

improved endurance. In addition to heavier total weapon 

loads, a larger aircraft could potentially carry larger 

individual weapons that would enable the aircraft to 

attack additional types of targets. For example, a wider 

array of targets would be vulnerable to an MQ-SX if that 

aircraft was designed to accommodate 2,000-pound class 

weapons, which are beyond the Reaper’s capacity.5

Higher speed enables an aircraft to spend a smaller proportion of its time in transit and more time on orbit and 

to increase the size of its orbit for surveillance. For example, if close support for ground forces required that an 

orbiting aircraft release a weapon no more than five 

minutes after receiving the order, a faster aircraft could 

respond from a greater distance. As a result, fewer aircraft 

might be required overall to cover a given area.

4. Department of Defense, Aircraft Procurement Plan: Fiscal Years 

2012–2041 (submitted with the 2012 budget, March 2011).

5. The Reaper can carry 3,000 pounds of weapons in all, but they 

must be distributed over four external carry points, thus limiting 

the weight of the heaviest weapon it can carry.
CHAPTER TWO POLICY OPTIONS FOR UNMANNED AIRCRAFT SYSTEMS 17

CBO

In brief, CBO compared the cost and capability (measured by payload-duration) of its options for the Air 

Force relative to those of the service’s current plan in 

2020 at three ranges: 275, 1,500, and 2,500 nautical 

miles (see Table 2-1). Option 1 would cost the same as 

the Air Force’s plan (by design) but would improve 

payload-duration by about 35 percent at intermediate 

range and reduce it by about 5 percent at short range; it 

would have no effect on long-range payload-duration. 

Option 2 would boost payload-duration even more—by 

about 67 percent at intermediate range and 17 percent at 

short range—but it would cost $2.9 billion more than 

Option 1 and the Air Force’s 2012 plan. Option 3 would 

save $3.7 billion relative to the plan but would reduce 

payload-duration by about 4 percent at short range, 17 

percent at intermediate range, and 45 percent at long 

range.

Option 1: Buy 224 MQ-SXs and 336 Fewer Reapers 

(Same Cost)

Under Option 1, the Air Force would replace purchases 

of 336 Reapers with 224 larger, more costly MQ-SX aircraft for roughly the same overall acquisition cost as in 

the service’s 2012 plan. Although the option would result 

in about 110 fewer multimission unmanned aircraft 

than in current plans—a reduction of about 20 percent—

payload-duration would be nearly equal to or better than 

in current plans because the faster transit time of the 

MQ-SX would increase the proportion of time on station 

(on orbit). Payload-duration would be about 35 percent 

higher at intermediate range and only a few percent lower 

than current plans at short range. 

The attractiveness of Option 1 depends on the usefulness 

of the additional payload and stealth features of the 

MQ-SX for future operations by unmanned aircraft. In 

light attack missions, unmanned aircraft are typically useful when a small number of precision weapons are sufficient—for example, when attacking terrorist hideouts or 

supporting small ground patrols that encounter unexpected resistance. Situations requiring heavier fire (for 

example, a major offensive) are often predictable, and 

support comes from more traditional means, such as 

ground artillery or manned strike aircraft. Even if the 

need for heavy fire is unexpected, lightly armed 

unmanned aircraft can serve as first responders, buying 

time until heavier support can arrive. 

The value of possible stealth features in new aircraft 

designs will similarly depend on how multimission 

unmanned operations evolve. Aircraft flying in the presence of advanced air defenses and having little or no support from forces designed to suppress or destroy those 

defenses require substantially more elaborate (and expensive) defensive features than do aircraft operating after air 

defenses have been neutralized. Furthermore, avoiding 

detection is more difficult for orbiting missions—such as 

those currently flown by Predators and Reapers in the 

uncontested airspace over Iraq and Afghanistan—because 

defenders have repeated opportunities to detect an aircraft and develop a picture of where and how the aircraft 

is being operated.6

 Current practices for unmanned aircraft may not be feasible in better-defended airspace, even 

when the aircraft have some stealth characteristics.

Option 2: Buy 336 MQ-SXs and 336 Fewer Reapers 

(Higher Cost)

The Air Force would buy 336 MQ-SXs and 336 fewer 

Reapers in Option 2. The number of aircraft (Reapers 

plus MQ-SXs) purchased each year would remain nearly 

unchanged through 2020 but would gradually shift from 

all Reapers in 2011 to all MQ-SXs in 2017. The total 

number of aircraft purchased would be about the same as 

under current plans, but the total cost would increase by 

about $2.9 billion.

Although the Air Force’s total inventory of MQ-type aircraft would remain essentially unchanged, the larger size 

and higher speed of the MQ-SX relative to the Reaper 

would result in a force capable of maintaining a payloadduration at a range of 1,500 nm that, by 2020, would be 

67 percent higher than that of the planned force. As in 

Option 1, the improved survivability of the MQ-SX, 

owing to its stealth features, could make it more useful in 

higher-threat environments.

6. The destruction of an F-117A stealth fighter over Serbia in 1999 

by a surface-to-air missile of older design may have resulted in part 

from intelligence reports that warned the defenders when F-117s 

were departing from Italy and in part from the Air Force’s use of 

predictable routes that allowed defenders to focus their defenses in 

a much smaller area. It may not be possible to make an unmanned 

aircraft stealthy enough to orbit for extended periods of time in 

well-defended airspace without being detected. CBO did not 

assess the stealth capabilities of the aircraft in relation to possible 

air defenses employed by future adversaries.
18 POLICY OPTIONS FOR UNMANNED AIRCRAFT SYSTEMS

CBO

Table 2-1. 

Differences Between Options for the Air Force and Its 2012 Plan, 2011 to 2020

Source: Congressional Budget Office.

Notes: Under all three options, the Air Force would buy new, stealthier aircraft, as follows:

• Option 1—Buy 224 MQ-SXs and 336 Fewer Reapers

• Option 2—Buy 336 MQ-SXs and 336 Fewer Reapers

• Option 3—Buy 24 MQ-SXs and 24 Fewer Global Hawks

n.a. = not applicable.

a. The MQ-SX is a notional aircraft that would have some characteristics consistent with ones under consideration for the Air Force’s 

proposed MQ-X. The MQ-SX postulated by CBO would be a jet-powered aircraft about one and a half times the size of the Reaper.

b. A wider array of targets would be vulnerable to an MQ-SX if it was designed to accommodate 2,000-pound weapons, which are beyond 

the Reaper’s capacity. The Reaper can carry 3,000 total pounds of weapons, but they must be distributed over four external carry points, 

which makes 750 pounds the heaviest weapon it can carry.

c. The MQ-SX would be designed to carry weapons, which the Global Hawk does not do.

d. Acquisition cost includes the cost of procuring air vehicles, sensors, and ground stations, plus the cost for research, development, test, 

and evaluation.

e. Payload-duration is the weight (payload) that an unmanned aircraft could carry to a location, multiplied by the amount of time the aircraft 

could stay there on orbit (duration).

Reaper 480 -336 -336 0

MQ-SXa 0 224 336 24

Global Hawk 28 0 0 -24

Improved Survivability with Stealth Features Yes

Increased Strike Capability Yes c

Acquisition Costd 20.4 0 2.9 -3.7

In 2015

At 275 nm n.a. -1 -1 -2

At 1,500 nm n.a. 4 4 -7

At 2,500 nm n.a. 0 0 -16

In 2020

At 275 nm n.a. -5 17 -4

At 1,500 nm n.a. 35 67 -17

At 2,500 nm n.a. 0 0 -45

Characteristics Compared with Plan

Difference in Number Purchased 

Air Force's Plan Option 1 Option 2 Option 3

Percentage Difference in Capability (Payload-duration)e

Difference in Cost (Billions of 2011 dollars)

n.a.

n.a.

Yes

Possibleb

Yes

Possibleb
CHAPTER TWO POLICY OPTIONS FOR UNMANNED AIRCRAFT SYSTEMS 19

CBO

Option 3: Buy 24 MQ-SXs and 24 Fewer Global 

Hawks (Lower Cost)

The Air Force would replace the remaining purchases of 

24 high-altitude Global Hawks with the same quantity of 

medium-altitude MQ-SXs, starting with purchases in 

2012. Although the Air Force would buy the same total 

number of aircraft as under current plans, the total cost 

would fall by about $3.7 billion.

Option 3 would reduce the overall payload-duration at all 

ranges (by 4 percent to 45 percent) because the MQ-SX 

is not as fast as the Global Hawk (and would therefore 

spend more time in transit between its airbase and orbit 

location) and has shorter endurance and a slightly smaller 

payload. However, the greater stealth—and thus 

improved survivability—of the MQ-SX compared with 

that of the Global Hawk could make it more useful in 

defended airspace, depending on the effectiveness of 

those defenses and the missions the aircraft was expected 

to perform. The need for unmanned aircraft to operate in 

defended airspace would depend on whether other 

weapon systems can take on that role.

A combination of Global Hawks and MQ-SXs would 

provide the long-range unmanned aircraft force with a 

mix of stealth capabilities. The existence of the recently 

acknowledged RQ-170 Sentinel indicates that the Air 

Force has already fielded such a mix.7 Option 3 would 

provide more stealthy aircraft overall.

The MQ-SX may not be able to carry all the specialized 

sensors that are planned for the later versions of the 

Global Hawk aircraft that they would replace under 

Option 3, although the MQ-SX would offer a strike 

capability that the Global Hawk does not. In its cost estimate for the MQ-SX, CBO assumed that the aircraft 

would be fielded with sensor systems consistent with 

MQ-type aircraft operations, not the more expensive systems currently carried by the Global Hawk. The MQ-SX 

should have sufficient capacity to carry the Global Hawk 

sensors, but the Air Force would have to purchase them 

and then integrate them into the aircraft, requiring further investment. In addition, some of the more expensive 

sensors, such as synthetic aperture radars, may not be useful on a stealthy aircraft if they emit signals that reveal the 

aircraft’s presence and possibly its location. 

Options for the Army

The Army’s current procurement plans for unmanned 

aircraft systems focus on small and medium-sized systems. The small systems use portable unmanned aircraft 

with handheld controls for tactical reconnaissance by 

frontline combat soldiers. Although the small systems are 

the most numerous type of unmanned aircraft systems in 

the Army’s inventory, they represent less than 10 percent 

of the service’s 2012 budget for such systems. CBO’s 

options for the Army focus on the medium-sized systems 

the service uses for reconnaissance and light attack missions. The aircraft and ground stations in those systems 

are more capable and also more expensive than the ones 

in small systems. 

CBO’s five options for the Army to purchase mediumsized unmanned aircraft look at the implications of three 

strategies: 

 Buying more-capable unmanned aircraft (Options 4 

and 5), 

 Buying a larger number of less-capable unmanned 

aircraft (Option 6), or 

 Changing the way unmanned aircraft are operated by 

conducting remote-split operations (Options 7 and 8).

CBO did not consider systems or advanced concepts that 

are in the early stages of development, such as the Long 

Endurance Multi-Intelligence Vehicle—an unmanned 

airship (an aircraft that is lighter than air) that the Army 

is currently investigating. In addition, CBO used shorter 

ranges (40, 275, and 650 nm) in analyzing options for 

the Army than it used for the Air Force because the 

Army’s missions for unmanned aircraft systems, such as 

supporting brigades and divisions, tend to require shorter 

ranges.

The first two options for the Army demonstrate the 

implications of purchasing the more capable (and more 

expensive) Reaper instead of the Grey Eagle (see 

Table 2-2). To keep the cost the same as in the Army’s 

plan, Option 4 would buy fewer Reapers than the number of Grey Eagles the Army plans to buy. It would boost 

capability (as measured by payload-duration) by 2020 by 

about 53 percent at short range (40 nm) and by about 

86 percent at long range (650 nm). 

7. Office of the Secretary of the Air Force, Directorate of Public 

Affairs, “RQ-170 Sentinel” (Air Force fact sheet, December 2, 

2010), www.af.mil/information/factsheets/factsheet

.asp?ID=16001.
20 POLICY OPTIONS FOR UNMANNED AIRCRAFT SYSTEMS

CBO

Table 2-2. 

Differences Between Options for the Army and Its 2012 Plan, 2011 to 2020

Source: Congressional Budget Office.

Notes: Under the options, the Army would buy more-capable aircraft (Options 4 and 5); buy more, less-expensive aircraft (Option 6); or 

change the way aircraft are operated (Options 7 and 8), as follows:

• Option 4—Buy 69 Reapers and 78 Fewer Grey Eagles

• Option 5—Buy 78 Reapers and 78 Fewer Grey Eagles

• Option 6—Buy 350 Firescouts and 78 Fewer Grey Eagles

• Option 7—Conduct Remote-Split Operations with 42 Fewer Grey Eagles

• Option 8—Conduct Remote-Split Operations with 36 Reapers and 78 Fewer Grey Eagles

n.a. = not applicable.

a. In remote-split operations, deployed divisions would have operational control of aircraft from a central fleet rather than be equipped with 

their own aircraft.

b. Tactical ground mobility is reduced because the Reaper cannot be carried on the Army’s standard tactical trucks.

c. The vertical takeoff and landing capability of the Firescout helicopter increases tactical flexibility.

d. Commonality between the Air Force (Reaper) and the Navy (Firescout) could lead to a future reduction in costs.

e. Acquisition cost includes the cost of procuring air vehicles, sensors, and ground stations, plus the cost for research, development, test, 

and evaluation. 

f. Payload-duration is the weight (payload) that an unmanned aircraft could carry to a location, multiplied by the amount of time the aircraft 

could stay there on orbit (duration).

g. The percentage change in payload-duration for Options 7 and 8 is shown for all divisions versus deployed divisions (all/deployed). For 

remote-split operations, payload-duration is lower than in the Army’s plan for divisions that are not deployed.

Grey Eagle 107 -78 -78 -78 -42 -78

Reaper 0 69 78 0 0 36

Firescout 0 0 035000

Adds Remote-Split Operationsa No No No Yes

Change in Tactical Flexibility Less b Less b More c Less b

Same Fuel Type No No No No

Increased Commonality with Other Servicesd Yes Yes Yes Yes

Acquisition Coste 5.9 0 0.5 0 -1.3 -1.0

In 2015

At 40 nm n.a. 60 60 -31 -19/0 g 13/51 g

At 275 nm n.a. 74 74 -49 -22/0 g 19/59 g

At 650 nm n.a. 95 95 -48 -22/0 g 31/74 g

In 2020

At 40 nm n.a. 53 67 60 -27/0 g 3/37 g

At 275 nm n.a. 65 82 -54 -30/0 g 7/42 g

At 650 nm n.a. 86 105 -54 -29/0 g 17/56 g

Percentage Difference in Capability (Payload-duration)f

Yes

No

Difference in Number Purchased 

Characteristics Compared with Plan

Difference in Cost (Billions of 2011 dollars)

Option 8

n.a.

n.a.

n.a.

n.a.

Yes

Same

Army's Plan Option 4 Option 5 Option 6 Option 7
CHAPTER TWO POLICY OPTIONS FOR UNMANNED AIRCRAFT SYSTEMS 21

CBO

Option 5 would provide even more capability but would 

cost $520 million more than the 2012 plan. By purchasing the same number of Reapers that the Army had 

planned for Grey Eagles, that option would provide 

nearly 67 percent more payload-duration at short range 

than the Army’s plan and about 105 percent more at long 

range. 

A third alternative for the Army, Option 6, would buy 

fewer medium-range aircraft and increase the number of 

shorter-range unmanned aircraft at the same cost as in 

the Army’s plan. Specifically, Option 6 would buy 

Firescout unmanned helicopters and fewer Grey Eagles, 

providing 60 percent more capability at short range but 

about one-half the capability of the Army’s planned force 

at long range. 

The other two options for the Army, Options 7 and 8, 

would centralize management of the Army’s mediumaltitude unmanned aircraft using an approach that has 

worked well for the Air Force. Instead of being equipped 

with their own aircraft, deployed divisions would be 

given operational control of aircraft from a central fleet, 

in a technique called remote-split operations. Although 

the aircraft would be under the control of the division 

commander, they could be operated over satellite links 

from the United States or other secure locations. Only 

the ground-support crews would deploy to the theater of 

operations with the unmanned aircraft; flight crews could 

remain in a central location. Remote-split operations 

would reduce the logistical burden that unmanned aircraft place on a deployed division, because much of the 

infrastructure for those aircraft could remain at their 

home base. By using remote-split operations, the Army 

could purchase fewer aircraft because the size of the fleet 

could be matched to the maximum number of divisions 

that might be deployed at any given time instead of to the 

total number of divisions in the Army’s force structure. 

Options 7 and 8 illustrate how the remote-split approach 

could reduce costs by using fewer Grey Eagles. Option 7 

would cost $1.3 billion less than the Army’s plan. Option 

8, which would purchase Reapers instead of Grey Eagles 

starting in 2012, would also reduce costs but by a smaller 

amount than in Option 7. 

With remote-split operations, the capability of deployed 

divisions in Option 7 would be the same as under the 

Army’s plan. Option 8 would increase the capability of 

the deployed divisions relative to Option 7 and still cost 

$1.0 billion less than the Army’s plan. Under both 

options, the capability of the overall force (including 

divisions not deployed) would be lower.

Option 4: Buy 69 Reapers and 78 Fewer Grey Eagles 

(Same Cost)

The Army would replace future purchases of 78 Grey 

Eagles with 69 larger, more costly Reaper aircraft for the 

same overall cost as in the 2012 plan. The 48 Grey Eagles 

purchased through 2011 would remain in service.

The Grey Eagle is an improved version of the Predator, 

but compared with the Reaper it is smaller and slower 

and has less range and payload capacity. The Army is 

developing the Grey Eagle as a unique version of the 

Predator to meet its own stated requirements. In particular, the Army requires that the Grey Eagle be able to take 

off and land automatically, be transportable on land via 

standard Army transport trucks, and burn the same heavy 

fuel as its ground vehicles (thereby avoiding the need to 

have two types of fuel on hand). 

The Reaper does not meet those requirements, but that 

may not be as large an issue as one might expect. The 

Reaper requires a conventional runway to take off and 

land, so transport must be available to take it to a suitable 

airfield. As currently designed, it is too big to fit on the 

Army’s standard tactical trucks, but it can travel on nontactical trucks such as tractor trailers. The Army does not 

intend to drive the trucks carrying the Grey Eagle or the 

Reaper cross-country on rough terrain, so transport using 

nontactical trucks should be feasible. In addition, Reapers 

use jet fuel rather than heavy fuel and operate out of fixed 

airbases where the same fuel is used by other aircraft, so 

the fact that the Reaper’s engines do not use heavy fuel 

may not pose a logistical problem. 

Being smaller and less powerful, the Grey Eagle can carry 

only about a quarter of the Reaper’s payload, and it also 

has a shorter range. Unless it uses a satellite relay, its range 

is limited to 275 nm by the need to maintain a line of 

sight with its data link. (When using its satellite relay, the 

Grey Eagle can increase its range to 650 nm.) The Reaper 

has a faster air speed than the Grey Eagle, which not only 

gives it more time to orbit in the target area (on station) 

because of a shorter transit time, especially at longer 

ranges, but also allows it to switch more quickly to other 

targets.

Both the Reaper and the Grey Eagle can carry weapons in 

addition to their surveillance equipment. The Reaper has 
22 POLICY OPTIONS FOR UNMANNED AIRCRAFT SYSTEMS

CBO

a larger maximum payload, however, and a longer time 

on station when equipped with weapons. The Grey 

Eagle’s effective range and time on station is sharply 

reduced when it carries weapons. For example, at a range 

of 68 nm, the Grey Eagle can remain on station for 

26 hours when performing surveillance without weapons. 

If it carries two Hellfire missiles—the usual payload in an 

armed reconnaissance mission—its time on station drops 

by nearly half, to 14 hours. If it carries four Hellfire missiles in an attack mission, the time on orbit drops even 

further, to 6 hours.

Compared with the Grey Eagle, the Reaper has shorter 

endurance when unarmed but longer endurance when 

carrying weapons. At the range of 68 nm, for example, 

the Reaper can perform unarmed surveillance for roughly 

20 hours, about 20 percent less time than the Grey Eagle. 

Its time on station for the armed reconnaissance mission 

(with two Hellfire missiles) is roughly 16 hours, compared with 14 hours for the Grey Eagle. It can stay on 

station about 13 hours for the attack mission—much 

longer than the 6 hours managed by the Grey Eagle. 

Furthermore, the Reaper can carry four Hellfire missiles 

plus two GBU-12 500-pound bombs for an attack mission, compared with only four Hellfire missiles for the 

Grey Eagle.

At longer ranges, where the Grey Eagle uses a satellite 

relay, the comparison is even more favorable to the 

Reaper. At 650 nm, the Grey Eagle can remain on station 

for about 14 hours for surveillance and about 3 hours for 

armed reconnaissance. It cannot perform the attack mission at that range because, with the extra payload, the 

transit time would be greater than the Grey Eagle’s overall 

endurance. By comparison, at that distance, the Reaper 

can remain on station for about 14 hours for surveillance, 

10 hours for armed reconnaissance, and 7 hours for 

attack. The Army does not claim any capability for Grey 

Eagle past 650 nm. By contrast, the Reaper can fly more 

than 1,600 nm, although it can perform a surveillance 

mission (without attack capability) for less than 2 hours 

at that range. 

Because of its greater range and endurance with a heavier 

payload, the Reaper provides more payload-duration at 

all ranges than the Grey Eagle. Under Option 4, total 

payload-duration would be 65 percent greater in 2020 at 

275 nm than under the Army’s plan and would exceed 

the capability in that plan at all other ranges as well. 

The Air Force is developing a new sensor called Gorgon 

Stare that will allow unmanned aircraft to observe a wider 

area by looking in several directions at once. An 

unmanned aircraft equipped with Gorgon Stare will 

potentially be more effective in surveillance missions, and 

the Air Force expects to equip some of its Reapers with 

the new sensor. The Grey Eagle cannot carry that sensor, 

and the Army plans to use Gorgon Stare on larger, 

manned surveillance aircraft.8

 If the Army purchased 

Reapers instead of Grey Eagles, it would be able to use 

Gorgon Stare on its unmanned aircraft too.

Another advantage of having the Army buy the Reaper 

as opposed to continuing to develop its own unique 

Grey Eagle system would be that it would increase 

commonality between Air Force and Army systems. That 

commonality could eventually reduce production costs 

because economies of scale affect the manufacturing 

process. Conversely, adding a new type of aircraft to the 

Army’s fleet could increase operating costs for training, 

spare parts, and tools. CBO did not include those savings 

or costs in its calculations.

Option 5: Buy 78 Reapers and 78 Fewer Grey Eagles 

(Higher Cost)

Under Option 5, the Army would replace planned future 

purchases of 78 Grey Eagles with the same number of 

larger, more costly Reapers. The Grey Eagles already purchased would remain in service, and the overall number 

of aircraft would remain the same. CBO estimates that 

this option would increase capability but would cost 

about $520 million more than the Army’s 2012 plan (see 

Table 2-2 on page 20).

As in Option 4, the Reaper provides greater capability 

than the Grey Eagle at all ranges. In this option, the 

payload-duration for the fleet at 650 nm would be 

105 percent greater in 2020 than under the current plan. 

Payload-duration in Option 5 would also exceed that in 

the Army’s plan at shorter ranges.

Option 6: Buy 350 Firescouts and 78 Fewer Grey 

Eagles (Same Cost)

This option would purchase 350 Firescout unmanned 

helicopters and would forgo buying 78 of the Grey Eagles 

in the Army’s 2012 plan. The total acquisition cost would 

8. Options involving manned aircraft that currently or might also 

perform reconnaissance missions were outside the scope of this 

study.
CHAPTER TWO POLICY OPTIONS FOR UNMANNED AIRCRAFT SYSTEMS 23

CBO

be about the same as in the Army’s plan. The Grey Eagles 

the Army has already purchased would remain in service.

In early 2009, the Army decided to cancel the brigadelevel Class IV Firescout unmanned aircraft system 

(similar to the Navy’s Firescout) as part of the cancellation of the Future Combat System. Because the Firescout 

is a small helicopter, it does not require a runway to 

operate, and the Army initially intended to have the 

system support brigades.9

 Option 6 replaces the divisionlevel Grey Eagle with the Firescout, which might be 

assigned to a division or to a brigade, although it lacks the 

long range that might be needed for some missions in a 

division’s typical area of responsibility.

The range and payload of the Firescout are much lower 

than those of the Grey Eagle, but because the Firescout is 

less costly, the Army could purchase many more of them. 

The resulting payload-duration in Option 6 would be 

nearly 60 percent greater than that in the Army’s plan in 

2020 at a range of 40 nm, but at longer ranges the 

payload-duration would be only about one-half that in 

the plan. Because of the time required to develop the 

aircraft, payload-duration would drop in 2014 and 2015 

as production of the Firescout got under way. 

The larger number of aircraft in Option 6 might make 

the overall force more resilient when sustaining losses 

from enemy activity or accidents. It would also distribute 

unmanned aircraft more densely across the battlefield, 

allowing more tactical units to receive dedicated 

unmanned aircraft support, compared with the support 

provided by smaller numbers of Grey Eagles. Because the 

Firescout does not require a runway, it may be able to 

operate closer to the supported units, thus compensating 

for its shorter range. That method of allocating assets 

might be better suited to supporting operations conducted by smaller military units scattered over a wide 

area, such as in the counterinsurgency operations in Iraq 

and Afghanistan. The Firescout might also be modified 

to carry a limited amount of supplies to soldiers in 

remote locations that have no access to runways. 

Another advantage of this option is that it would allow 

the Army and the Navy to share a common aircraft. In its 

analysis, however, CBO did not consider any cost savings 

that might be gained from that commonality. More 

unmanned aircraft in the air at any time will require more 

ground stations and controllers. Although the cost estimates for this option include the costs of procuring those 

extra systems, they do not reflect the potential increase in 

operation and support costs that the Army would incur as 

a result of the extra systems and personnel.

Option 7: Conduct Remote-Split Operations with 

42 Fewer Grey Eagles (Lower Cost)

Under this option, the Army would adopt the Air Force’s 

approach of using remote-split operations and buy 

42 fewer Grey Eagles to take advantage of efficiencies that 

such an approach would provide. Specifically, the Army 

would buy 65 new, enhanced Grey Eagles instead of 107 

under its current plan; it would also have the 48 already 

purchased (including 24 slightly less capable early 

versions). That fleet of 113 medium-sized unmanned 

aircraft would provide enough capacity to support six 

divisions on the ground (the peak U.S. deployment in 

Operation Iraqi Freedom) and three additional divisions 

in special operations or training. Any unused aircraft 

would be held in reserve. The reduced fleet of Grey 

Eagles would cost $1.3 billion less than the Army’s plan, 

assuming that the production rate remained the same but 

ended in 2012.

The Army plans to assign 12 Grey Eagles to up to 10 of 

its combat divisions and to retain additional sets for special operations forces and training; the Grey Eagles would 

operate from locations in the combat theater, usually 

using line-of-sight control from their own division.10 By 

contrast, the Air Force operates its medium-sized and 

large unmanned aircraft systems from the continental 

United States or Europe using remote-split operations. 

(For a comparison of line-of-sight and remote-split 

operations, see Figure 2-1.) The Air Force uses line of 

sight only during takeoff and landing, the points at which 

controllers in the combat theater operate the aircraft. The 

9. The most recent plan, in 2009, was to buy five systems 

(20 Firescout helicopters) for each of the 73 brigades in the 

Army as a whole (active plus National Guard), for a total of 

1,460 aircraft. However, another plan in some Army documents 

stated that the service would purchase eight systems (32 aircraft) 

for each of the Army brigades, for a total of 2,336 aircraft. See 

Andrew Feickert, The Army’s Future Combat System: Background 

and Issues for Congress, CRS Report for Congress RL32888 

(Congressional Research Service, August 3, 2009), p. 8.

10. The Grey Eagle system includes a satellite relay for longer-range 

operations in the combat theater. 
24 POLICY OPTIONS FOR UNMANNED AIRCRAFT SYSTEMS

CBO

Figure 2-1.

Methods of Controlling Unmanned Aircraft Systems in a Combat Theater

Source: Congressional Budget Office.

Mobile Ground

Control Station

Launch and Recovery

Element

Unmanned Aircraft

Ground Forces

Target

Video Only

Launch and Recovery

Element

Unmanned Aircraft

Ground Forces

Video Only Target

Fixed Ground 

Control Station

Fixed Satellite

Relay

Terrestrial

Circuits

Outside Combat Theater

Satellite

Line-of-Sight Operations

Remote-Split Operations

Sensor Data

(Video and

aircraft control)

Sensor Data Aircraft Control Signals
CHAPTER TWO POLICY OPTIONS FOR UNMANNED AIRCRAFT SYSTEMS 25

CBO

Air Force then transfers control of the aircraft and sensors 

to operators in the United States using satellite communications links. The need for local Air Force controllers 

could be reduced further if the Air Force adopted the 

automatic takeoff and landing system it is currently 

developing for its unmanned aircraft, but some ground 

crews would always have to be deployed with the aircraft 

to service them between missions. 

The Army rarely deploys all its divisions at one time, and 

divisions that are not deployed do not need extensive 

unmanned aircraft support except for training purposes. 

A small set of unmanned aircraft employed continuously 

in a remote-split operation might be able to provide the 

same amount of support to military units that are 

deployed as would a larger fleet of unmanned aircraft 

assigned to all divisions simultaneously, whether the 

divisions were deployed or not. 

This option would use fewer unmanned aircraft systems—and therefore fewer operators and ground-support 

soldiers—than does the Army’s plan. However, the 

unmanned aircraft could potentially be operated for longer periods under this option because they would remain 

in the combat theater to support newly deployed units 

while other units returned home. The reduced set of 

deployed soldiers providing ground support, who service 

and maintain the unmanned aircraft systems, would 

rotate as needed, perhaps on a separate schedule from the 

soldiers in the rotating combat units. The option might 

require extra sets of ground crews compared with current 

plans in order to maintain fresh crews deployed in the 

combat theater, but most of the unmanned aircraft operators and intelligence operators would remain in the 

United States. 

The Army prefers to have its divisional unmanned 

aircraft systems under the control of the division commander they support. Option 7 would maintain that 

control relationship: Although the option would not 

locate the medium-sized unmanned aircraft systems 

with their division, the systems would remain under 

that division’s operational control.

Under this option, the smaller Army fleet of mediumsized unmanned aircraft would have lower payloadduration at all ranges compared with the 2012 plan. 

However, a portion of the smaller fleet of aircraft in this 

option would be based in the combat theater rather 

than with each division whether or not the division was 

deployed, and the option would therefore provide the 

same capability in the combat theater as the Army’s 

2012 plan.

Option 8: Conduct Remote-Split Operations with 

36 Reapers and 78 Fewer Grey Eagles (Lower Cost)

Option 8 is similar to Option 7 in that the Army would 

adopt remote-split operations but differs by buying 

78 fewer Grey Eagles and adding 36 Reapers. As a result, 

this option would also yield a fleet of 113 medium-sized 

unmanned aircraft but with a different composition: 36 

Reapers, 29 new Grey Eagles, and the 48 Grey Eagles 

already purchased (including 24 slightly less capable early 

versions of Grey Eagles).

As in Option 7, a fleet of that composition would be able 

to support six divisions on the ground and three additional divisions in special operations or training, and any 

unused aircraft would be held in reserve. As in Options 4 

and 5, this option has the possible disadvantage that the 

Reaper requires a different type of fuel than the Army’s 

ground vehicles use (jet fuel instead of heavy fuel), but it 

does use the same fuel as the Army’s other aircraft. A 

Reaper on its transport truck is also less mobile than a 

Grey Eagle on an Army tactical truck, but that reduced 

mobility may not be an issue because the aircraft can be 

remotely based at locations with better road networks.

The reduced set of Reapers and Grey Eagles under 

Option 8 would cost $1.0 billion less than the Army’s 

2012 plan. The fleet would have more capability 

(payload-duration) than Option 7 and the Army’s plan 

after 2015 because it would include Reapers instead of 

Grey Eagles. In terms of the payload-duration of aircraft 

provided in the combat theater to deployed forces, 

Option 8 would have 37 percent to 56 percent more 

capability in 2020 than under the 2012 plan even though 

it would have 42 fewer aircraft overall.

CBO

Appendix:

Missions Conducted by 

Unmanned Aircraft Systems and 

Reasons for Using Them

The Department of Defense (DoD) defines an 

unmanned aerial vehicle as “a powered, aerial vehicle that 

does not carry a human operator, uses aerodynamic forces 

to provide vehicle lift, can fly by itself (autonomously) or 

be remotely piloted, can be expendable or recoverable at 

the end of flight, and can carry a lethal or nonlethal 

payload.” DoD further specifies that “ballistic and semiballistic missiles, cruise missiles, and artillery projectiles 

are not considered unmanned aircraft vehicles.”1

 The 

term “unmanned aerial vehicle” is the current official 

DoD nomenclature that has replaced the previously (but 

still commonly) used term “remotely piloted vehicle.” 

This Congressional Budget Office study uses the term 

“unmanned aircraft system” to emphasize the fact that 

those complex systems include ground stations and other 

components besides the aircraft itself.

Such unmanned systems can undertake various missions, 

although the analysis in this study focuses primarily on 

capabilities for reconnaissance and light attack missions. 

Because they are unmanned, the aircraft can sometimes 

undertake new types of missions, reduce the risks of traditional missions, and potentially lower costs relative to 

manned missions. The types of missions a system will 

perform shape the requirements for endurance, speed, 

altitude, and payload—all of which affect the system’s 

cost.

Although unmanned aircraft systems do not carry a 

person on board, in most cases they are piloted and 

usually need personnel at a ground station to operate the 

aircraft and the systems, such as sensors, that the aircraft 

carries. Current policy requires a human operator to fire 

weapons carried on unmanned aircraft. Ground operators 

rely on communications systems to send control 

commands to the aircraft and to receive flight and sensor 

data from it. The communications links can require a 

significant amount of data, the ability to transfer it 

rapidly (bandwidth), or both—especially for full-motion 

video and broad-spectrum signal intelligence missions (in 

which the system monitors enemy signals)—potentially 

complicating or limiting operations. 

For long-distance missions in which the unmanned 

aircraft are beyond the controllers’ line of sight, intermediate communications relays are necessary, usually in 

the form of satellites. Operations are not always possible 

where those satellite links do not exist: Some aircraft 

intended for use close to the ground station are not 

equipped for satellite communications, and the line-ofsight limitations of their communications system confine 

them to operating over smaller areas. In addition, the 

time lag associated with lengthy communications links 

usually results in a corresponding lag between a controller’s input and the aircraft’s response. Such time lags can 

be problematic for missions, such as air-to-air combat, 

that may require near-instantaneous reaction time on the 

part of a remote operator.

1. Department of Defense, DoD Dictionary of Military and Associated Terms, Joint Publication 1-02 (November 8, 2010, as 

amended through January 31, 2011), www.dtic.mil/doctrine/

dod_dictionary/. 
28 POLICY OPTIONS FOR UNMANNED AIRCRAFT SYSTEMS

CBO

Types of Missions

The analysis in this study focuses on the capabilities of 

unmanned aircraft systems for reconnaissance and light 

attack missions. The systems can also be used in a wide 

variety of other missions. The intended missions have 

critical implications for the systems’ complexity and cost.

Reconnaissance

Most unmanned aircraft systems perform reconnaissance 

missions, using sensors to detect and observe objects on 

land or sea or to intercept and analyze electronic emissions from ground, sea, or air sources. Although the aircraft component of an unmanned aircraft reconnaissance 

system is important, the sensors and communications 

equipment are equally vital and can dictate the system’s 

overall performance. Sensors used on unmanned aircraft 

must balance the need for high resolution or sensitivity 

with the demands for the smallest possible system that 

will fit into the available aircraft and not add too much 

weight to the payload.

The performance of an unmanned aircraft system 

depends on the combination of the altitude at which it 

flies and the resolution and sensitivity of its sensors. In 

general, aircraft that fly at higher altitudes require larger 

sensors with higher resolution and sensitivity. Smaller systems that fly at lower altitudes can use smaller sensors and 

still be effective. 

A subset of reconnaissance, force protection, is a form of 

sentry duty that may be performed by an unmanned aircraft system. Small, low-altitude systems usually perform 

that mission, although sometimes a medium-sized system 

is employed. 

Light Attack

Unmanned aircraft systems that carry weapons—called 

multipurpose systems by the Air Force—have proved to 

be effective in attacking ground targets. They can be 

configured to carry fewer or more weapons depending on 

their mission; the weight of the weapons payload affects 

the aircraft’s endurance (that is, how long it can stay in 

the air). In an armed reconnaissance mission, an 

unmanned aircraft carries a few weapons in case it needs 

to strike an unpredictable target, but the emphasis is on 

reconnaissance and endurance. Conversely, in an attack 

mission, an unmanned reconnaissance aircraft carries a 

full load of weapons, which reduces its endurance but 

enables it to destroy a particular target. 

Electronic Warfare

Unmanned aircraft can be extremely useful in electronic 

warfare, especially when acting as airborne communications relays and when gathering signal intelligence. They 

may also be able to function as airborne jammers and 

electronic decoys. Those missions are an important part 

of the overall intelligence-gathering effort.

By virtue of the high altitude at which they fly and their 

long endurance, unmanned aircraft systems can be effective communications relays. An airborne unmanned aircraft with proper equipment can extend the range of 

communications for tactical systems.2

 The extended 

communications range is especially useful when military 

units using low-power portable tactical radios operate 

over a widely dispersed area, as is typical in counterinsurgency warfare.

Gathering information by listening to enemy radios and 

monitoring enemy radars is an important mission in 

modern combat operations, including counterinsurgency.3

 Insurgent fighters use not only mobile and 

satellite phones for communication but also sophisticated 

military radios. Intercepting their communications and 

analyzing the content is therefore essential to locating 

them.4

 Unmanned aircraft systems can be very useful in 

such intelligence-gathering missions because the high 

altitude at which they fly and the length of time they can 

stay in one place makes it possible to intercept most 

signals from a very long range. However, some electronic 

signals are too weak to reach an aircraft flying at a high 

altitude; intercepting weaker signals requires a receiver 

flying at a lower altitude that can operate closer to the 

signal’s source. Because of those technological limitations, 

it is impossible to design a single solution for all of the 

military’s signal intelligence missions.

2. For example, the Army’s Shadow unmanned aircraft system can 

use a Harris Falcon III radio to relay both tactical Single Channel 

Ground and Airborne Radio System (SINCGARS) signals and 

ultrahigh frequency signals to a distance of 95 miles (82 nautical 

miles). See Joris Janssen, “Harris Radio on UAV Provides Aerial 

Comms Relay for U.S. Army,” Aviation Week and Space Technology

(blog entry, February 15, 2008).

3. Department of the Army, Counterinsurgency, Field Manual 3-24 

(December 15, 2006), Appendix E.

4. Usman Ansari, “Pakistan Puts UAVs at Center of Technology 

Effort,” Defense News, November 10, 2008, www.defensenews.com/story.php?i=3811950. 
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Other Missions

Unmanned aircraft systems have the potential to perform 

a number of other missions normally associated with 

manned aircraft, such as search and rescue; mapping; 

bomb detection and destruction; firefighting; reconnaissance for nuclear, chemical, or biological weapons of mass 

destruction; support of special operations; marine interdiction (preventing ships from entering a sea area); 

emplacement of obstacles, such as mines; and 

psychological warfare. 

Impact of Missions on System Requirements

For missions that require operating from an airbase at a 

greater distance from the target location or remaining on 

station for a greater length of time, longer endurance is 

needed. Missions that may involve rapid shifts of location 

benefit from higher speeds, which allow aircraft to spend 

less time in transit from their airbase to a surveillance 

orbit, or from one orbit to another.

Some missions are best accomplished with a greater field 

of view from a given location, and flying at higher altitudes can provide that capability. For example, the maximum line of sight from an aircraft flying at 60,000 feet to 

a target at sea level is nearly 500 kilometers (km), meaning that objects on the ground within that radius would 

be potentially in view of the aircraft’s sensors. The 

corresponding maximum line of sight for an aircraft 

flying at 30,000 feet would be about 350 km. Greater 

line of sight offers the potential to view a larger area 

from a given location, which can be particularly important if the unmanned aircraft is looking into areas that lie 

within restricted airspace (across international borders, 

for example).

Operating at a higher altitude and greater range requires a 

larger payload to carry more-sophisticated but heavier 

sensors, because smaller, lighter sensors have a limited 

ability to gather detailed information at such long ranges. 

The more-capable sensors have to accommodate larger, 

higher-resolution cameras, for example, or larger antenna 

arrays for detecting electronic emissions; the sensors are 

therefore heavier and require more power to run. Meeting 

the size, weight, and power demands of more-capable 

sensors requires larger (and more expensive) aircraft. 

Reasons for Using Unmanned Systems

For many missions, the complications inherent in operating an aircraft without a pilot (in particular, the need for 

ground stations and the transmission of large amounts of 

data via satellite) are worth the effort. However, the 

advantages—enabling new missions by overcoming physical constraints, reducing risks to pilots, and lowering the 

cost of aircraft—are also accompanied by disadvantages.

Enabling New Missions

An aircraft’s performance is often constrained by the 

physical limits of the human body. In aerial combat, for 

example, high-g maneuvers—which subject the aircraft 

and pilot to accelerations many times the force of gravity—might be necessary when engaging with an enemy 

fighter or trying to avoid enemy fire from the ground. 

The greater maneuverability that could be included in the 

design of an unmanned aircraft might be useful in some 

circumstances. Consequently, extreme maneuverability is 

a characteristic that may be incorporated into future 

generations of unmanned strike aircraft or unmanned 

fighters.5

Most of today’s larger unmanned aircraft systems (and 

those planned for the future) take advantage of the 

absence of a human crew to accomplish longer and moredangerous missions. Although aerial refueling can extend 

the flight range of a manned aircraft, the length of time 

the aircraft can be kept in the air is primarily constrained 

by the endurance of its crew. The Air Force estimates a 

limit of about 12 hours for the pilot of single-seat aircraft 

(such as a fighter or a U-2 reconnaissance aircraft). 

Longer missions are possible if multiple crew members 

are on board. For example, B-2 strategic bombers flew 

round-trip missions of greater than 30 hours from 

Whiteman Air Force Base in Missouri to strike targets in 

Kosovo in the 1990s and flew similar missions to Iraq in 

2003 and to Libya in 2011. To accomplish those missions, a third pilot accompanied the two primary crew 

members to relieve them and prevent fatigue. Having 

accommodations for extra crew members requires a much 

larger (and thus more expensive) aircraft than the mission 

might otherwise need. The Air Force estimates that even 

when crews are rotated, 40 hours is the longest a manned 

5. Some proponents think that unmanned aircraft will eventually be 

able to engage in full-fledged air-to-air combat. Although it is 

unlikely that such combat could be undertaken by unmanned 

systems in the near future, a stealthy unmanned fighter equipped 

with air-to-air radar and weapons could carry out simpler missions 

such as detecting and shooting at other aircraft. Therefore, 

unmanned strike aircraft might eventually be equipped with a 

limited air-to-air capability for self-defense.
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mission could last. Such long flights also expend the 

pilots’ allowance for flight hours per day and month and 

so raise costs for manpower.6

The nature and duration of missions carried out by 

reconnaissance aircraft have changed over time. In the 

past, the most common missions—those that involved 

flying to a target, photographing it, and returning to 

base—usually required between 12 and 40 hours of flight 

time with aerial refueling to reach any location on Earth. 

In 2011 and beyond, however, the armed services expect 

a greater emphasis on keeping aircraft continuously on 

surveillance over areas of interest. Much of that emphasis 

stems from recent counterinsurgency operations in Iraq 

and Afghanistan, where aircraft conducting surveillance 

missions have proved to be effective against “fleeting” targets that appear unexpectedly and then quickly return to 

hiding.7

 Those “persistence” missions give commanders 

not only an almost real-time view of areas of interest but 

also the ability to rapidly target a specific location for 

observation or attack because an aircraft is always in the 

vicinity. In many cases, even a slow aircraft such as the 

Predator, if it is orbiting nearby, can provide a quicker 

response than a faster manned aircraft that might need to 

be called from some distance away.

Of course, manned aircraft can be (and have been) used 

for that type of persistent reconnaissance or strike coverage. Large aircraft such as the E-3 Airborne Warning and 

Control System (AWACS) and the E-8 Joint Surveillance 

and Target Attack Radar System (JSTARS), which have 

the potential to rotate crews and refuel in flight, can 

remain aloft for extended periods. For example, JSTARS 

missions over Iraq have typically lasted between 10 and 

20 hours. The military, however, has only a small number 

of those aircraft—they are costly to build and operate, 

they are vulnerable to antiaircraft weapons and therefore 

can operate only in secure airspace, and they do not carry 

weapons. Although they also provide surveillance of large 

areas of sky or ground, their sensors have typically not 

been appropriate for the type of surveillance and targeting needed in counterinsurgency operations, which focus 

on individuals or small groups.

Fighter aircraft have been used when necessary to provide 

persistent coverage (for both reconnaissance and attack 

missions) in areas where threats from air defenses are or 

might be present and where multiple surveillance orbits 

must be flown to ensure that aircraft are close enough to 

rapidly reach any location where they might be needed. 

Because fighters fly faster and can reach targets more 

quickly, they can operate in more widely separated areas 

than can slower aircraft, reducing the number of orbits 

needed. But fighters also have shorter endurance than 

current unmanned aircraft, and flying the smaller number of orbits might require a larger number of fighters.8

Other disadvantages of using fighter aircraft in persistent 

orbits include the need for extensive tanker support for 

aerial refueling, the rapid expenditure of aircrews’ allowed 

flying hours, and the draw of fighter resources away 

from other missions.9

Reducing Risks

Unmanned aircraft are useful in situations in which the 

likelihood is high that the aircraft could be lost to enemy 

fire or in which the diplomatic consequences of an aircrew’s being captured would be sufficiently serious to 

deter the use of manned aircraft even if the chance of loss 

was low. Suppressing enemy air defenses is a particularly 

hazardous mission; aircraft assigned to that mission must 

seek out and engage enemy surface-to-air missiles or airdefense artillery sites and suppress or destroy them. 

Although some aircraft might be destroyed in a successful 

suppression campaign, overall aircraft losses would be 

lower because the aircraft that followed would be able to 

6. Department of Defense, Unmanned Aircraft Systems Roadmap, 

2005–2030 (August 4, 2005), p. 2. 

7. In the past, orbiting missions could be accomplished only in 

the absence of effective enemy air defenses. As a result, they 

were not emphasized in planning for conventional force-on-force 

conflicts, which were DoD’s primary focus. In the current 

counterinsurgencies in Iraq, Afghanistan, and Pakistan, there 

are no effective enemy air defenses, and even slow unmanned 

aircraft can fly with relatively little risk of being shot down.

8. The number of aircraft needed to maintain a continuous orbit for 

24 hours a day depends on many factors, including the distance of 

the orbit from the airbase, transit speed, endurance, and maintenance time between missions. In addition, weapons payload 

might be a factor if targets arise frequently enough to exhaust 

an aircraft’s store of weapons before it reaches the limit of its 

endurance.

9. In addition to limits on the maximum duration of a sortie (that is, 

a mission or attack by a single plane), medically established limits 

are also imposed on the total number of hours aircrews can fly 

over any 30- or 90-day period. A crew’s performance has been 

shown to degrade with too much flying, although the limits can 

be relaxed or waived if necessary during wartime. Experience with 

current counterinsurgency operations suggests that operators of 

unmanned aircraft systems might require similar limits.
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attack their assigned targets with increased chances of 

survival. Reflecting the importance placed on those 

missions, the air campaigns over Bosnia and Kosovo and 

the Northern/Southern Watch operations in Iraq saw 

nearly one-quarter of air-combat missions dedicated to 

suppressing air defenses.10 The services are exploring 

unmanned aircraft systems that would have the necessary 

speed, stealth characteristics, targeting systems, and 

weapons to successfully attack modern air-defense 

systems.

Reconnaissance missions in areas that have capable and 

active air defenses can also be among the most hazardous. 

For those missions, aircraft—in many cases flying 

unarmed and alone—operate over enemy territory to collect information from photographs, radar images, or electronic signals about enemy activity. In the Vietnam and 

Arab–Israeli Wars, aircraft and aircrews on reconnaissance 

missions suffered the highest loss rates.11

Even in peacetime, manned aircraft conducting reconnaissance missions have been shot down or otherwise 

lost. The loss or capture of a pilot (and other aircrew 

members) in those circumstances can have profound diplomatic implications beyond the single reconnaissance 

mission. For example, the downing of a U-2 aircraft in 

1960 and the forced landing of an EP-3E Aries II electronic surveillance aircraft in China in 2001 illustrate the 

political costs of losing manned aircraft on reconnaissance missions. In contrast to the diplomatic crises associated with those events, the losses of seven unmanned 

Firebee and D-21 aircraft over China during the 1970s 

and of numerous Predators over Iraq, Afghanistan, and 

Pakistan in recent years were almost unnoticed beyond 

the countries’ militaries; similarly, the shooting down of 

an Iranian Ababil 3 unmanned aircraft by the United 

States over Baghdad in February 2009 was not a major 

diplomatic event.12

A risk associated with any aircraft is the unintended 

civilian casualties that sometimes accompany airstrikes. 

Unmanned airstrikes, by the nature of their centralized 

control, tend to receive closer scrutiny by the military 

chain of command before a target is engaged than do 

strikes by traditional manned aircraft or missiles. That 

higher level of oversight should reduce unintended 

casualties, but it may not eliminate the problem. Many 

analysts believe that using unmanned aircraft systems in 

counterinsurgency operations to strike targets without 

first cross-checking and coordinating target data with 

either the host country or other information sources can 

lead to civilian casualties. Some observers state that 

unmanned aircraft systems cannot be expected to conduct strike missions without appropriate ground-based 

intelligence support, although the problem also applies to 

manned aircraft strikes.13

Potentially Lowering Costs

Unmanned aircraft systems are usually less expensive than 

manned aircraft. Initial concepts envisioned very lowcost, essentially expendable aircraft. As of 2011, however, 

whether substantially lower costs will be realized is 

unclear. Although a pilot may not be on board, the 

advanced sensors carried by unmanned aircraft systems 

are very expensive and cannot be viewed as expendable. 

In addition, the design of unmanned aircraft systems 

must be safe and reliable enough not to pose an unacceptable danger to forces operating with them. For example, 

an unmanned aircraft built to operate from an aircraft 

carrier must be able to land no less safely and reliably 

than its manned counterpart.

Moreover, excessively high losses of aircraft can negate 

cost advantages by requiring the services to purchase large 

numbers of replacement aircraft. Early unmanned aircraft 

systems were plagued by high attrition rates because of 

problems with the reliability of engines and difficulties 

with remotely piloted takeoffs and landings in which 

operators lacked the “seat-of-the-pants” feel available to a 

pilot in an aircraft. The MQ-1 Predator, which has a 

single engine and few redundant avionics systems, had 

an accident rate of 28 mishaps per 100,000 flight hours 

during its early deployment—more than triple the rate of 

8.2 per 100,000 flight hours for general aviation singlepiston engine aircraft. The Air Force has been able to 

reduce the accident rate on the Predator to 7.6 mishaps 

per 100,000 flight hours by providing more training to 

10. Christopher Bolkcom, Military Suppression of Enemy Air Defenses 

(SEAD): Assessing Future Needs, CRS Report for Congress 

RS21141 (Congressional Research Service, May 11, 2005). 

11. Department of Defense, Unmanned Aircraft Systems Roadmap, 

2005–2030, p. 2.

12. Rod Nordland and Alissa Rubin, “U.S. Says It Shot Down an 

Iranian Drone Over Iraq,” New York Times, March 17, 2009, 

p. A10 (New York edition).

13. Jane Perlez, “Pakistan Rehearses Its Two-Step on Airstrikes,” New 

York Times, April 16, 2009, p. A10 (New York edition). 
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operators and by improving data links and other aspects 

of reliability.14 With the introduction of the larger and 

more capable MQ-9 Reaper, the Air Force has adopted a 

more conventional approach and now includes reliability 

systems such as triple-redundant flight controls and backup communications links, but such systems increase the 

cost of the aircraft. New technologies, such as an automated landing capability, offer the potential to further 

reduce losses due to accidents.

Unmanned aircraft systems operating in civilian airspace 

also need high levels of reliability to ensure the safety 

of people on the ground and in other aircraft. Aircraft 

developers are therefore adding expensive systems to 

unmanned aircraft—such as sense-and-avoid cameras, 

transponders, and improvements in airworthiness and 

reliability—to meet the Federal Aviation Administration’s 

requirements for certification.

The support systems required for unmanned aircraft, 

such as ground stations, add costs that are not associated 

with manned aircraft. For example, in the Air Force’s 

2010 budget request, funding for ground stations and 

communications systems for the Reaper was about 

10 percent of the funding requested for the aircraft themselves. Of course, ground stations should not experience 

much, if any, attrition. Consequently, average expenditures on ground stations per aircraft purchased will probably decrease once DoD has reached its desired inventory. 

Future unmanned aircraft could also be designed to operate with existing (perhaps slightly modified) ground 

stations.

Part of the difficulty in comparing the cost of unmanned 

aircraft systems with their manned equivalents is identifying a manned equivalent. The absence of accommodations for a pilot is not the only reason aircraft like the 

Reaper are about one-sixth the cost of the F-16. The F-16 

is many times faster, is much more maneuverable, and 

can carry much heavier payloads than the Reaper. Consequently, although the Reaper might be more efficient 

than the fighter in an orbiting role in support of ground 

troops when only small numbers of weapons are needed, 

it cannot accomplish most of the other missions required 

of fighters (notably air-to-air combat). 

The cost of manned combat aircraft in 2011 is in part the 

product of several decades of incorporating multiple 

capabilities into each aircraft. The intention was to 

reduce the overall number of aircraft and pilots required, 

thereby defraying the costs of the new aircraft. Although 

that logic may have held true for conflicts between conventional military forces (in which an aircraft could be 

confronted with a capable adversary at any time), some 

aspects of the new counterinsurgency operations may be 

more efficiently accomplished by more-specialized 

unmanned aircraft.

Having specialized unmanned aircraft systems can also 

reduce costs. For example, those aircraft can substitute for 

expensive, high-performance aircraft, such as fighters, in 

orbiting missions that do not require great speed or 

maneuverability. The services have expressed concern 

about the increased wear and tear that operations in Iraq 

and Afghanistan have placed on fighter (and other) aircraft. In addition to having lower operating costs per 

flight hour, specialized unmanned aircraft systems can 

reduce flight hours for fighter aircraft and thereby 

decrease replacement costs over time.

14. Eric Mathewson, Colonel, U.S. Air Force, “MQ-1B Predator and 

MQ-9 Reaper” (program briefing for Congressional Budget 

Office staff, June 2009).
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Glossary

acquisition cost: the cost of procuring air vehicles, 

sensors, and ground stations, plus the cost for research, 

development, test, and evaluation.

duration: the amount of time an aircraft can be kept on 

orbit.

endurance: the total amount of time an unmanned 

aircraft can stay in the air.

ground station: the location from which the flight of an 

unmanned aircraft is controlled and from which the data 

it collects is analyzed and displayed.

line of sight: an unobstructed optical or electromagnetic 

path between a sensor and a target.

on station: on orbit.

orbit: an unmanned aircraft patrol over a geographically 

or electronically defined location. Most unmanned 

aircraft rely on forward motion for lift and thus must 

circle to stay over a particular area. 

payload-duration: the weight (payload) that an aircraft 

could carry to a location, multiplied by the amount of 

time the aircraft could stay there on orbit (duration).

payload: the amount of weight (weapons, sensors, and so 

on) that an unmanned aircraft can carry.

range: the distance from the originating airbase to the 

orbit location, expressed in nautical miles.

remote-split operations: operations in which deployed 

divisions would have operational control of aircraft from 

a central fleet rather than be equipped with their own 

aircraft.

transit time: the time it takes an aircraft to travel from the 

airbase to the orbit location and back.

unmanned aircraft: a powered, aerial vehicle that does 

not carry a human operator, uses aerodynamic forces to 

provide vehicle lift, can fly autonomously or be piloted 

remotely, can be expendable or recoverable, and can carry 

a lethal or nonlethal payload. Ballistic or semiballistic 

vehicles, cruise missiles, and artillery projectiles are not 

considered unmanned aerial vehicles. 

unmanned aircraft system (UAS): an unmanned 

aircraft plus the necessary equipment, communications 

network, ground stations, personnel, and infrastructure 

to control it.