2-1 

 

Chapter 2
 

Introduction 

The en route phase of flight is defined as that segment of 

flight from the termination point of a departure procedure 

to the origination point of an arrival procedure. The 

procedures employed in the en route phase of flight are 

governed by a set of specific flight standards established 

by 14 CFR [Figure 2-1], FAA Order 8260.3, and related 

publications. These standards establish courses to be flown, 

obstacle clearance criteria, minimum altitudes, navigation 

performance, and communications requirements. 

En Route Operations 
 

Figure 2-1. Code of Federal Regulations, Title 14 Aeronautics and Space. 

En Route Navigation 

En route instrument flight rules (IFR) navigation is evolving 

from the ground-based navigational aid (NAVAID) airway 

system to a sophisticated satellite and computer-based 

system that can generate courses to suit the operational 

requirements of almost any flight. The FAA Global 

Navigation Satellite System (GNSS) provides satellite-based 

positioning, navigation, and timing services in the United 

States to enable performance-based operations for all 

phases of flight, to include en route navigation. 

14 CFR Part 91, § 91.181, is the basis for the course to be 

flown. Unless authorized by ATC, to operate an aircraft 

within controlled airspace under IFR, pilots must either 

fly along the centerline when on a Federal airway or, 

on routes other than Federal airways, along the direct 

course between NAVAIDs or fixes defining the route. The 

regulation allows maneuvering to pass well clear of other 

air traffic or, if in visual meteorogical conditions (VMC), 

to clear the flightpath both before and during climb or 

descent. 

Airways 

Airway routing occurs along pre-defined pathways called 

airways. [Figure 2-2] Airways can be thought of as threedimensional highways for aircraft. In most land areas of 

the world, aircraft are required to fly airways between the 

departure and destination airports. The rules governing 

airway routing, Standard Instrument Departures (SID) 

and Standard Terminal Arrival (STAR), are published flight 

procedures that cover altitude, airspeed, and requirements 

for entering and leaving the airway. Most airways are 

eight nautical miles (14 kilometers) wide, and the airway 

flight levels keep aircraft separated by at least 500 vertical 

feet from aircraft on the flight level above and below 

when operating under VFR. When operating under IFR, 

between the surface and an altitude of Flight Level (FL) 

290, no aircraft should come closer vertically than 1,000 

feet. Above FL 290, no aircraft should come closer than 

2,000 feet except in airspace where Reduced Vertical 

Separation Minima (RVSM) can be applied in which case 

the vertical separation is reduced to 1,000 feet. Airways 

usually intersect at NAVAIDs that designate the allowed 

points for changing from one airway to another. Airways 

have names consisting of one or more letters followed by 

one or more digits (e.g., V484 or UA419). 

The en route airspace structure of the National Airspace 

System (NAS) consists of three strata. The first stratum low 

Figure 2-2. Airways depicted on an aeronautical chart. 

2-2 
 

altitude airways in the United States can be navigated 

using NAVAIDs, have names that start with the letter V, and 

are called Victor Airways. [Figure 2-3] They cover altitudes 

from approximately 1,200 feet above ground level (AGL) 

up to, but not including 18,000 feet above mean sea level 

(MSL). The second stratum high altitude airways in the 

United States all have names that start with the letter J, 

and are called Jet Routes. [Figure 2-4] These routes run 

from 18,000 feet to 45,000 feet. The third stratum allows 

random operations above flight level (FL) 450. The altitude 

separating the low and high airway structure varies from 

county to country. For example, in Switzerland it is 19,500 

feet and 25,000 feet in Egypt. 

Air Route Traffic Control Centers 

The FAA defines an Air Route Traffic Control Center (ARTCC) 

as a facility established to provide air traffic control (ATC) 

service to aircraft operating on IFR flight plans within 

controlled airspace, principally during the en route phase 

of flight. When equipment capabilities and controller 

workload permit, certain advisory/assistance services may 

be provided to VFR aircraft. 

ARTCCs, usually referred to as Centers, are established 

primarily to provide air traffic service to aircraft operating 

on IFR flight plans within the controlled airspace, and 

principally during the en route phase of flight. There are 

Figure 2-3. Victor airways. Figure 2-4. Jet routes. 

ZID 

ZMP 

ZOB 

ZBW 

ZNY 

ZNY 

ZDC 

ZAU 

ZKC 

ZME 

ZTL 

ZJX 

ZMA 

ZHU 

ZFW ZAB 

ZDV 

ZLA 

ZOA 

ZLC 

ZSE 

ZHN 

ZAN 

Cleveland Center 

Albuquerque Center 

Seattle Center 

Atlanta Center 

Chicago Center 

Boston Center 

Washington

Center (DC) 

Denver Center 

Fort Worth Center 

Houston Center 

Indianapolis

Center 

Jacksonville Center

 Kansas City Center 

Los Angeles Center 

Salt Lake City Center 

Miami Center 

Memphis Center 

Minneapolis Center 

New York 

Oakland Center Center

Honolulu 

Center 

Anchorage

Center 

Figure 2-5. Air Route Traffic Control Centers. 

2-3 
 

 

 

21 ARTCC’s in the United States. [Figure 2-5] Any aircraft 

operating under IFR within the confines of an ARTCC’s 

airspace is controlled by air traffic controllers at the Center. 

This includes all sorts of different types of aircraft: privately 

owned single engine aircraft, commuter airlines, military 

jets, and commercial airlines. 

The largest component of the NAS is the ARTCC. Each 

ARTCC covers thousands of square miles encompassing 

all or part of several states. ARTCCs are built to ensure safe 

and expeditious air travel. All Centers operate 7-days a 

week, 24-hours a day, and employ a combination of several 

hundred ATC specialists, electronic technicians, computer 

system specialists, environmental support specialists, and 

administrative staff. Figure 2-6 is an example of the Boston 

ARTCC. The green lines mark the boundaries of the Boston 

Center area, and the red lines mark the boundaries of 

Military Operations Areas (MOAs), Prohibited, Restricted, 

Alert, and Warning Areas. 

Safe Separation Standards 

The primary means of controlling aircraft is accomplished 

by using highly sophisticated computerized radar systems. 

In addition, the controller maintains two-way radio 

communication with aircraft in his or her sector. In this 

way, the specialist ensures that the aircraft are separated 

by the following criteria: 

• Laterally—5 miles 

• Vertically— 

•	 1,000 feet (if the aircraft is below FL 290, or 

between FL 290 and FL 410 for RVSM compliant 

aircraft) 

•	 2,000 feet (if the aircraft is at FL 290 or above) 

The controllers can accomplish this separation by issuing 

instructions to the pilots of the aircraft involved. Altitude 

assignments, speed adjustments, and radar vectors are 

examples of instructions that might be issued to aircraft. 

En route control is handled by pinpointing aircraft positions 

through the use of flight progress strips. These strips are 

pieces of printed paper containing pertinent information 

extracted from the pilot’s flight plan. These strips are printed 

20 minutes prior to an aircraft reaching each Center’s sector. 

A flight progress strip tells the controller everything needed 

to direct that aircraft. If the flight progress strips of each 

aircraft approaching a sector are arranged properly, it is 

possible to determine potential conflicts long before the 

aircraft are even visible on the Center controller’s display. 

In areas where radar coverage is not available, this is the 

sole means of separating aircraft. 

Figure 2-6. Boston Air Route Traffic Control Center. 

The strips, one for each en route point from which the 

pilot reports his or her position, are posted on a slotted 

board in front of the air traffic controller. [Figure 2-7] At a 

glance, he or she is able to see certain vital data: the type 

of aircraft and who is flying it (airline, business, private, 

or military pilot), aircraft registration number or flight 

number, route, speed, altitude, airway designation, and the 

estimated time of arrival (ETA) at destination. As the pilot 

calls in the aircraft’s position and time at a predetermined 

location, the strips are removed from their slots and filed. 

Any change from the original flight plan is noted on the 

strips as the flight continues. Thus, from a quick study of 

the flight progress board, a controller can assess the overall 

traffic situation and can avoid possible conflicts. 

Figure 2-7. Flight progress strips. 

2-4 
 

 

Figure 2-8. Fort Worth Air Route Traffic Control Center. 

Figure 2-8 shows the Fort Worth, Texas Air Route Traffic 

Control Center (ZFW) and the geographical area that it 

covers. The Center has approximately 350 controllers. Most 

are certified and some are in on-the-job training. 

Sectors 

The airspace controlled by a Center may be further 

administratively subdivided into smaller, manageable 

pieces of airspace called sectors. A few sectors extend from 

the ground up, but most areas are stratified into various 

levels to accommodate a wide variety of traffic. Each sector 

is staffed by a set of controllers and has a unique radio 

frequency that the controller uses to communicate with 

the pilots. As aircraft transition from one sector to another, 

they are instructed to change to the radio frequency used 

by the next sector. Each sector also has secure landline 

communications with adjacent sectors, approach controls, 

areas, ARTCCs, flight service centers, and military aviation 

control facilities. 

Figure 2-9. Low altitude sectors. 

Figure 2-10. Intermediate altitude sectors. 

Figure 2-11. High altitude sectors. 

Figure 2-12. Ultra high altitude sectors. 

The ARTCC at Fort Worth, Texas is subdivided into sectors 

that are categorized as follows: 

2-5 
 

 

 

 

• Eighteen low altitude sectors. [Figure 2-9] 

• Seven intermediate altitude sectors. [Figure 2-10] 

• Sixteen high altitude sectors. [Figure 2-11] 

• One ultra high altitude sector. [Figure 2-12] 

From one to three controllers may work a sector, depending 

upon the amount of air traffic. Each controller is assigned 

to work the positions within an area of specialization. 

Controllers have direct communication with pilots, with 

surrounding sectors and Centers, plus the towers and Flight 

Service Stations (FSS) under their jurisdiction. Each control 

position is equipped with computer input and readout 

devices for aircraft flight plan data. 

The Center controllers have many decision support 

tools (computer software programs) that provide vital 

information to assist the controllers in maintaining safe 

separation distances for all aircraft flying through their 

sector. For example, one tool available allows the controller 

to display the extended route of any aircraft on the radar 

screen called a vector line. This line projects where the 

aircraft will be within a specified number of minutes, 

assuming the aircraft does not change its course. This is 

a helpful tool to determine if aircraft flying intersecting 

routes pass safely within the separation standard, or if they 

conflict with each other. In addition to vector lines, the 

controller can also display a route line for any given aircraft 

on his or her radar screen. This tells the controller where 

a particular aircraft is in specified number of minutes, as 

well as the path the aircraft will fly to get there. Decision 

support tools such as these help each controller look ahead 

and avoid conflicts. 

In-flight Requirements and Instructions 

The CFRs require the pilot in command under IFR in 

controlled airspace to continuously monitor an appropriate 

Center or control frequency. When climbing after takeoff, 

an IFR flight is either in contact with a radar-equipped local 

departure control or, in some areas, an ARTCC facility. As 

a flight transitions to the en route phase, pilots typically 

expect a handoff from departure control to a Center 

frequency if not already in contact with the Center. 

The FAA National Aeronautical Information Services 

publishes en route charts depicting Centers and sector 

frequencies. [Figure 2-13] During handoff from one Center 

to another, the previous controller assigns a new frequency. 

In cases where flights may be out of range, the Center 

frequencies on the face of the chart are very helpful. In 

Figure 2-13, notice the boundary between Memphis, 

Tennessee and Atlanta, Georgia Centers, and the remote 

sites with discrete very high frequency (VHF) and ultra high 

frequency (UHF) for communicating with the appropriate 

NOT FOR NAVIGATION MEMPHIS

Huntsville

120.8 307.0

ATLANTA

Chattanooga

132.05 353.8

MEMPHIS

ATLANTA

Figure 2-13. Air Route Traffic Control Centers and sector frequencies. 

2-6 
 

 

 

 

 

ARTCC. These Center frequency boxes can be used for 

finding the nearest frequency within the aircraft range. 

They also can be used for making initial contact with the 

Center for clearances. The exact location for the Center 

transmitter is not shown, although the frequency box is 

placed as close as possible to the known location. 

During the en route phase, as a flight transitions from one 

Center facility to the next, a handoff or transfer of control 

is required as previously described. The handoff procedure 

is similar to the handoff between other radar facilities, such 

as departure or approach control. During the handoff, 

the controller whose airspace is being vacated issues 

instructions that include the name of the facility to contact, 

appropriate frequency, and other pertinent remarks. 

Accepting radar vectors from controllers does not relieve 

pilots of their responsibility for safety of flight. Pilots must 

maintain a safe altitude and keep track of their position, 

and it is their obligation to question controllers, request 

an amended clearance, or, in an emergency, deviate from 

their instructions if they believe that the safety of flight 

is in doubt. Keeping track of altitude and position when 

climbing, and during all other phases of flight, are basic 

elements of situational awareness (SA). Aircraft equipped 

with an enhanced ground proximity warning system 

(EGPWS), terrain awareness and warning system (TAWS), 

or traffic alert and collision avoidance system (TCAS) help 

pilots detect and/or correct for potential unsafe proximities 

to other aircraft and increases pilot(s) situational awareness. 

Regardless of equipment, pilots must always maintain SA 

regarding their location and the location of traffic in their 

vicinity. 

High Altitude Area Navigation Routing 

Special high altitude routes allow pilots routing options for 

flight within the initial high altitude routing (HAR) Phase 

I expansion airspace. Pilots are able to fly user-preferred 

routes, referred to as non-restrictive routing (NRR), between 

specific fixes described by pitch (entry into) and catch (exit 

out of) fixes in the HAR airspace. Pitch points indicate an 

end of departure procedures, preferred IFR routings, or 

other established routing programs where a flight can 

begin a segment of NRR. The catch point indicates where 

a flight ends a segment of NRR and joins published arrival 

procedures, preferred IFR routing, or other established 

routing programs. 

The HAR Phase I expansion airspace is defined as that 

airspace at and above FL 350 in fourteen of the western 

and southern ARTCCs. The airspace includes Minneapolis 

(ZMP), Chicago (ZAU), Kansas City (ZKC), Denver (ZDV), 

Salt Lake City (ZLC), Oakland (ZOA), Seattle Centers (ZSE), 

Los Angeles (ZLA), Albuquerque (ZAB), Fort Worth (ZFW), 

Memphis (ZME), and Houston (ZHU). Jacksonville (ZJX) 

and Miami (ZMA) are included for east-west routes only. 

To develop a flight plan, select pitch and catch points 

which can be found in the Chart Supplement (CS) based 

upon your desired route across the Phase I airspace. Filing 

requirements to pitch points, and from catch points, remain 

unchanged from current procedures. For the portion of the 

route between the pitch and catch points, NRR is permitted. 

Where pitch points for a specific airport are not identified, 

aircraft should file an appropriate departure procedure (DP), 

or any other user preferred routing prior to the NRR portion 

of their routing. Where catch points for a specific airport 

are not identified aircraft should file, after the NRR portion 

of their routing, an appropriate arrival procedure or other 

user preferred routing to their destination. 

Additionally, information concerning the location and 

schedule of special use airspace (SUA) and Air Traffic 

Control Assigned Airspace (ATCAA) can be found at http:// 

sua.faa.gov. ATCAA refers to airspace in the high altitude 

structure supporting military and other special operations. 

Pilots are encouraged to file around these areas when they 

are scheduled to be active, thereby avoiding unplanned 

reroutes around them. 

In conjunction with the HAR program, area navigation 

(RNAV) routes have been established to provide for a 

systematic flow of air traffic in specific portions of the en 

route flight environment. The designator for these RNAV 

routes begin with the letter Q, for example, Q-501. Where 

those routes aid in the efficient orderly management of air 

traffic, they are published as preferred IFR routes. 

Preferred IFR Routes 

Preferred IFR routes are established between busier airports 

to increase system efficiency and capacity. They normally 

extend through one or more ARTCC areas and are designed 

to achieve balanced traffic flows among high density 

terminals. IFR clearances are issued on the basis of these 

routes except when severe weather avoidance procedures 

or other factors dictate otherwise. Preferred IFR routes are 

listed in the CS and can also be found on www.fly.faa.gov, 

which requires entering the following data: departure 

airport designator, destination, route type, area, aircraft 

types, altitude, route string, direction, departure ARTCC, 

and arrival ARTCC. [Figure 2-14] If a flight is planned to or 

from an area having such routes but the departure or arrival 

point is not listed in the CS, pilots may use that part of a 

preferred IFR route that is appropriate for the departure or 

arrival point listed. Preferred IFR routes are correlated with 

departure procedures (DPs) and STARs and may be defined 

by airways, jet routes, direct routes between NAVAIDs, 

2-7 
 

 

Figure 2-14. Chart Supplement (includes Airport/Facility Directory 

section). 

waypoints, NAVAID radials/ distance measuring equipment 

(DME), or any combinations thereof. 

Preferred IFR routes are published in the CS for the low and 

high altitude stratum. If they begin or end with an airway 

number, it indicates that the airway essentially overlies 

the airport and flights normally are cleared directly on the 

airway. Preferred IFR routes beginning or ending with a fix 

indicate that pilots may be routed to or from these fixes 

via a SID route, radar vectors, or a STAR. Routes for major 

terminals are listed alphabetically under the name of the 

departure airport. Where several airports are in proximity, 

they are listed under the principal airport and categorized as

 a metropolitan area (e.g., New York Metro Area). One way 

preferred IFR routes are listed is numerically, showing the 

segment fixes and the direction and times effective. Where 

more than one route is listed, the routes have equal priority 

for use. Official location identifiers are used in the route 

description for very high frequency omnidirectional ranges 

(VORs) and very high frequency omnidirectional ranges/ 

tactical air navigation (VORTACs), and intersection names 

are spelled out. The route is direct where two NAVAIDs, an 

intersection and a NAVAID, a NAVAID and a NAVAID radial 

and distance point, or any navigable combination of these 

route descriptions follow in succession. 

A system of preferred IFR routes helps pilots, flight crews, 

and dispatchers plan a route of flight to minimize route 

changes, and to aid in the efficient, orderly management 

of air traffic using Federal airways. Preferred IFR routes 

are designed to serve the needs of airspace users and 

to provide for a systematic flow of air traffic in the major 

terminal and en route flight environments. Cooperation by 

Figure 2-15 Preferred IFR routes. 

2-8 
 

all pilots in filing preferred routes results in fewer air traffic 

delays and better efficiency for departure, en route, and 

arrival air traffic service. [Figure 2-15] 

Substitute Airway or Route Structures 

ARTCCs are responsible for specifying essential substitute 

airway or route segments (sub-routes) and fixes for use 

during scheduled or unscheduled VOR/VORTAC shutdowns. 

Scheduled shutdowns of navigational facilities require 

planning and coordination to ensure an uninterrupted 

flow of air traffic. Aeronautical Information Services, in 

coordination with the ARTCCs, determine when the length 

of outages or other factors require publication of subroutes and Flight Program Operations (AJW-3) provides 

flight inspection services, obstacle clearance verification, 

certification, and final approval of substitute routes. 

Substitute Airway En Route Flight Procedures 

A schedule of proposed facility shutdowns within the region 

is maintained and forwarded as far in advance as possible 

to enable the substitute routes to be published. Substitute 

routes are normally based on VOR/VORTAC facilities 

established and published for use in the appropriate 

altitude strata. In the case of substitute routes in the upper 

airspace stratum, it may be necessary to establish routes by 

reference to VOR/VORTAC facilities used in the low altitude 

system. Non-directional (radio) beacon (NDB) facilities may 

only be used where VOR/VORTAC coverage is inadequate 

and ATC requirements necessitate use of such NAVAIDs. 

Where operational necessity dictates, NAVAIDs may be 

used beyond their standard service volume (SSV) limits that 

define the reception limits of unrestricted NAVAIDs, which 

are usable for random/unpublished route navigation, 

provided that the routes can be given adequate frequency 

protection. 

Uncontrolled airspace 

BCD vortac (shutdown) 

ABC vortac 

Sub-route V-98 

CDE vortac 

V-98 

V-98 

Obstacle study and flight 

inspection of sub-route required 

(Centerline must be in 

controlled airspace) 

Figure 2-16 14 CFR Part 95 sub-routes. 

Uncontrolled airspace 

BCD vortac (shutdown) 

ABC vortac 

Off-airway sub-route 

CDE vortac 

V-98 

V-98 

Obstacle study and flight 

inspection of sub-route required 

Figure 2-17 Non-Part 95 sub-routes. 

2-9 
 

 

GHI vortac HIJ vortac IJK vortac (L)

V-204 V-204 

30 

70 

Obstacle study flight 

inspection and ESV’s 

required 

GHI vortac IJK vortac (L) 

HIJ vortac (shutdown) 

SUB-ROUTE V-204 

60* 

90 

Figure 2-18 Sub-route wider than existing route. 

The centerline of substitute routes must be contained 

within controlled airspace [Figure 2-16], although substitute 

routes for off-airway routes may not be in controlled airspace. [Figure 2-17] Substitute routes are flight inspected 

to verify clearance of controlling obstacles and to check for 

satisfactory facility performance. If substitute routes do not 

overlie existing routes, or are wider than existing routes, 

map studies are required to identify controlling obstacles. 

[Figure 2-18] The format for describing substitute routes 

is from navigational fix to navigational fix. A minimum en 

route altitude (MEA) and a maximum authorized altitude 

(MAA) are provided for each route segment. Temporary 

reporting points may be substituted for the out-of-service 

facility and only those other reporting points that are 

essential for ATC. Normally, temporary reporting points 

over intersections are not necessary where Center radar 

coverage exists. A minimum reception altitude (MRA) is 

established for each temporary reporting point. 

Tower En Route Control 

Tower en route control (TEC) is an ATC program available 

to pilots that provides a service to aircraft proceeding to 

and from metropolitan areas. It links designated approach 

control areas by a network of identified routes made up 

of the existing airway structure of the NAS, which makes 

it possible to fly an IFR flight without leaving approach 

control airspace. [Figure 2-19] This service is designed 

to help expedite air traffic and reduces ATC and pilot 

communication requirements. The program is generally 

used by non-turbojet aircraft operating at and below 

10,000 feet but a few facilities, such as Milwaukee and 

Chicago, have allowed turbojets to proceed between 

city pairs. Participating flights are relatively short with a 

duration of two hours or less. 

TEC is referred to as tower en route, or tower-to-tower, and 

allows flight beneath the en route structure. TEC reallocates 

airspace both vertically and geographically to allow flight 

planning between city pairs while remaining with approach 

control airspace. All users are encouraged to use the TEC 

route descriptions located in the CS when filing flight plans. 

[Figure 2-20] All published TEC routes are designed to avoid 

en route airspace, and the majority is within radar coverage. 

Tower En Route Control Route Descriptions 

The graphic depiction of TEC routes located in the CS is not 

to be used for navigation or for detailed flight planning 

because not all city pairs are depicted. The information 

is intended to show geographic areas connected by TEC. 

[Figure 2-19] Pilots should refer to the route descriptions 

for specific flight planning. 

As shown in Figure 2-20, the route description contains four 

columns of information. The first column is the approach 

control area within which the departure airport is located, 

which are listed alphabetically. The second column shows 

the specific route, airway, or radial that is to be used. 

The third column shows the highest altitude allowed for 

2-10 
TOWER EN ROUTE CONTROL (TEC) 

Northeast U.S. (Eastern) 

(Lines connecting airports 

depict adjacent approach 

control facilities) 

CLE 

Radar approach control area 

PIT 

CKB 

ROA 

RIC 

IAD 

HAR 

RDG 

ABE 

NYC 

ACY 

PHL WRI

BWI 

DOV 

AVP 

BGM 

ELM 

DCA 

PXT 

ORF 

CRW 

GSO 

ERI 

BUF 

YNG 

CAK 

HTS 

DC 

PENNSYLVANIA 

WEST VIRGINIA 

VIRGINIA 

MARYLAND NEW JERSEY 

DELAWARE 

LEGEND 

Figure 2-19. Tower En Route Control (TEC) Northeast U.S. (Eastern). 

the route, and the fourth shows the destination airport, 

which are also listed alphabetically. When flight planning, 

it is important to always check current publications for 

information about the departure and destination airport. 

Routes are effective only during each respective terminal 

facilities normal operating hours. Always check NOTAMs 

to ensure that appropriate terminal facilities are operating 

for the planned flight time. Altitudes are always listed in 

thousands of feet. ATC may request that the pilot changes 

altitude while in flight in order to maintain the flight within 

approach control airspace. ATC provides radar monitoring 

and, if necessary, course guidance if the highest altitude 

assigned is below the MEA. 

Shown in Figure 2-21, under the second column, the word 

“Direct” appears as the route when radar vectors are used 

or no airway exists. This also indicates that a SID or STAR 

may be assigned by ATC. When a NAVAID or intersection 

identifier appears with no airway immediately preceding 

or following the identifier, the routing is understood to be 

direct to or from that point unless otherwise cleared by ATC. 

Routes beginning and ending with an airway indicate that 

the airway essentially overflies the airport, or radar vectors 

are issued. [Figure 2-21] Where more than one route is listed 

to the same destination, ensure that the correct route for 

the type of aircraft classification has been filed. These are 

denoted after the route in the altitude column using J (jet 

powered), M (turbo props/special, cruise speed 190 knots 

or greater), P (non-jet, cruise speed 190 knots or greater), 

or Q (non-jet, cruise speed 189 knots or less). [Figure 2-22] 

Although all airports are not listed under the destination 

column, IFR flights may be planned to satellite airports in 

the proximity of major airports via the same routing. When 

filing flight plans, the coded route identifier (i.e., BURL 1, 

VTUL4, or POML3) may be used in lieu of the route of flight. 

2-11 
 

 

 

 

 

Highest 

Route 

Altitude Destination 

............ V93 LRP V39 ETX 

7000 Allentown 

............ V268 LEEAH V229 

7000 Atlantic City 

............ V268 ENO V16 JFK V229 HFD CLOWW (Single 7000 Bangor

 engine and /E, /F. /G only) 

............ V268 ENO V16 JFK V229 HFD CLOWW (Single 7000 Bar Harbor

 engine and /E, /F. /G only) 

............ V93 LRP V499 

7000 Binghamton 

............ V268 ENO V16 JFK V229 

7000 Boston (North)

 HFD HFDO53 DREEM (Single engine only) 

............ V268 ENO V16 JFK V229 HFD V3 WOONS 7000 Boston 

 (Single engine only) 

............ V268 ENO V16 JFK V229 BDR BDR014 

7000 Boston

 JUDDS (Single engine only) 

............ V268 ENO V16 JFK V229 BDR (Single 7000 Bradley

 engine only) 

............ V268 ENO V16 JFK V229 BDR (Single 7000 Bridgeport

 engine only) 

............ V31 HAR 

7000 Capital City 

............ V268 ENO 

7000 Dover AFB 

............ V44 MRB 

6000 Dulles 

............ V268 ENO V16 JFK V229 BRD MAD 

7000 Groton

 MAD126 MONDI (Single engine only) 

TOWER EN ROUTE CONTROL 

Approach Control Area

(Including Satellites)

Baltimore 

Highest 

Route 

Altitude Destination 

............ EJC V149 LHY 

8000 Albany 

............ ETX LHY 

8000 Albany 

............ V149 MAZIE ARD CYN 

5000 Atlantic City 

............ V93 LRP 

8000 Baltimore 

............ EXT V162 DUMMR V93 LRP 

6000 Baltimore 

............ V39 LRP 

8000 Baltimore 

............ V130 

10000 Bradley 

............ Direct 

10000 Bradley 

............ FJC STW 

5000 Caldwell 

............ (2) EXT V30 SBJ 

5000 Farmingdale 

............ ETX V162 HAR 

8000 Harrisburg 

............ Direct 

10000 Hartford 

............ EXT ETX004 WEISS 

4000 Hazleton 

............ EXT V39 

4000 Lancaster 

TOWER EN ROUTE CONTROL 

Approach Control Area

(Including Satellites)

Allentown 

Figure 2-20. Chart Supplement (NE), Tower En Route Control route descriptions (Baltimore). 

Figure 2-21. Chart Supplement (NE), Tower En Route Control route descriptions (Allentown). 

2-12 
 

 

 

Highest 

Route 

Altitude Destination 

............ V229 DIXIE V276 ARD 

6000 Allentown 

............ V1 DIXIE V276 ARD (Single engine only) 

6000 Allentown 

............ V1 ATR V308 OTT 

4000 Andrews, AFB 

............ LEEAH V268 BAL 

4000 Baltimore 

............ V1 JFK V229 HFD CLOWM (Single engine and 6000 Bangor

 /E, /F, /G only) 

............ V1 JFK V229 HFD CLOWM (Single engine and 6000 Bar Harbor

 /E, /F, /G only) 

............ V1 JFK V229 HFD HFD053 DREEM (Single 6000 Boston (North)

 (Single engine only) 

............ V1 JFK V229 HFD V3 WOONS (Single engine 6000 Boston

 only 

............ V1 JFK V229 HFD FOSTY WOONS (Single 6000 Boston

 engine only) 

............ V1 JFK V229 BDR BDR14 JUDDS (Single 6000 Bradley

 engine only) 

............ V184 ZIGGI JFK 210 JFK V229 BDR (Twins 6000 Bridgeport

 only, n/a between 1400-2100) 

............ HOWIE V1 JFK V229 BDR (Single engine only) 6000 Bridgeport 

............ V184 00D DQO V469 HAR 

4000 Capital City 

TOWER EN ROUTE CONTROL 

Approach Control Area

(Including Satellites)

Atlantic City 

Figure 2-22. Chart Supplement (NE), Tower En Route Control route descriptions (Atlantic City). 

Airway and Route System 

There are three fixed route systems established for 

air navigation purposes. They are the Federal airway 

consisting of VOR (low victor airways, high jet routes), 

NDB (low or medium frequency) and the RNAV route 

system. To the extent possible, these route systems are 

aligned in an overlying manner to facilitate transition 

between each. The majority of the airways are made up 

of victor airways, jet routes, and RNAV, but some low/ 

medium frequency (L/MF) airways and routes are still 

being used in Alaska and one other that is located off 

the coast of North Carolina and is called Green 13 (G13). 

[Figure 2-23] 

Airway/Route Depiction 

IFR en route charts show all IFR radio NAVAIDs that have 

been flight-checked by the FAA and are operational. The 

FAA, Aeronautical Information Services publishes and 

distributes U.S. Government Civil Aeronautical Charts and 

flight information publications. IFR en route navigation 

information is provided on three charts: IFR en route low 

Figure 2-23. Low frequency airway G13. altitude chart, IFR en route high altitude chart, and Terminal 

Area Chart (TAC). [Figure 2-24A and B] 

2-13 
 

Figure 2-24. IFR en route low altitude (left) and high altitude (right) charts. 

IFR En Route Low Altitude Chart 

En route low altitude charts provide aeronautical 

information for navigation under IFR conditions below 

18,000 feet MSL. Low altitude charts [Figure 2-25] include 

the following information: 

•	 Airways [Figure 2-25A] 

•	 RNAV routes [Figure 2-25B] 

•	 Limits of controlled airspace [Figure 2-25C] 

•	 VHF radio aids to navigation (frequency, identification, 

channel, geographic coordinates) [Figure 2-25D] 

•	 Airports that have an instrument approach procedure 

or a minimum 3,000 foot hard surface runway 

[Figure 2-25E] 

•	 Off-route obstruction clearance altitudes (OROCA) 

[Figure 2-25F] 

•	 Reporting points [Figure 2-25G] 

•	 Special use airspace areas [Figure 2-25H] 

•	 Military training routes [Figure 2-25I] 

IFR aeronautical charts depict VOR airways (airways based 

on VOR or VORTAC NAVAIDs) in black, identified by a “V” 

(Victor) followed by the route number (e.g., V12). [Figure 

2-26] LF/MF airways (airways based on LF/MF NAVAIDs) 

are sometimes referred to as colored airways because they 

are identified by color name and number (e.g., Amber One, 

charted as A1). Green and red airways are plotted east and 

west, and amber and blue airways are plotted north and 

south. Regardless of their color identifier, LF/MF airways 

are depicted in brown. [Figure 2-27] 

Airway/route data, such as the airway identifications, 

bearings or radials, mileages, and altitude (e.g., MEA), 

minimum obstacle clearance altitude (MOCA), and MAA, 

are shown aligned with the airway and in the same color 

as the airway. [Figure 2-26] 

All airways/routes that are predicated on VOR or VORTAC 

NAVAIDs are defined by the outbound radial from the 

NAVAID. Airways/routes that are predicated on LF/MF 

NAVAIDs are defined by the inbound bearing. 

New low altitude RNAV routes have been created by the 

FAA. RNAV routes provide more direct routing for IFR 

aircraft and enhance the safety and efficiency of the NAS. In 

order to utilize these routes, aircraft must be equipped with 

IFR approved GNSS. In Alaska, when using RNAV routes, the 

aircraft must be equipped with Technical Standing Order 

(TSO)-145a and 146a equipment. 

Low altitude RNAV only routes are identified by the letter 

“T” prefix, followed by a three digit number (T-200 to T-500). 

RNAV routes are depicted in aeronautical blue, as well as the 

RNAV route data, which includes the following [Figure 2-28]: 

•	 Route line 

•	 Identification boxes 

2-14 
 

 

122.4

H

2-15 

Figure 2-25. Information found on en route low altitude charts. 

Figure 2-26. Victor airways. 

Figure 2-27. LF/MF airways. 

E VALENTINE 

Miller Fld 

(VTN) 

2596 47 L 

VALENTINE

 314 VTN 

V60

29 

26 

35 

10000

V190 

53 

27 

153 

TAFOY 

F 

x 

232 

154 

152

9 

D 

L 83 

28.55 

G 

A 

V4 

30 

Victor Route (with RNAV/GPS 

MEA shown in blue) 

*35 00

 3 50 0G

 S 50 0 

310 

B 

T270

70 

5000G 

*5400

6000G 

087 

67

268 088

NGOZI 

GRANT 

269

T270 

Waypoint 

Magnetic reference bearing 

C 

Hot Springs Muni 

(HSR) 

3150 45 L 

AINSWORTH

 112.7 ANW 74 N42°34.15' W99°59.38' 

H 

COLUMBUS 

122.4 D 

086 

248 

+ 

H 

P-00 

R-000 

W-000 

A-000 

CYR-000 

CYA-000 

(MU) D-000 

SPECIAL USE AIRSPACE 

WALL 1 

MOA 

WALL 2 

MOA 

Exclusion area and note 

Line delimits 

internal separation 

of same special 

use area or 

exclusion areas 

I 

IR-15-17

 AINSWORTH

114.0 MAI 87

N30°47.17' W85°07.47' 

GAINESVILLE 
Figure 2-28. Low altitude RNAV routes. 

• Mileages 

• Waypoints 

• Waypoint names 

• Magnetic reference bearings 

• MEAs 

Magnetic reference bearings are shown originating from a 

waypoint, fix/reporting point, or NAVAID. A GNSS MEA for 

each segment is established to ensure obstacle clearance 

Figure 2-29. Low altitude RNAV route data. 

and communications reception. All MEAs are identified 

with a “G” suffix. [Figure 2-29] 

Joint Victor/RNAV routes are depicted using black for 

the victor airways and blue for the RNAV routes, and the 

identification boxes for each are shown adjacent to one 

another. Magnetic reference bearings are not shown. MEAs 

are stacked in pairs or in two separate columns, GNSS 

and Victor. On joint routes, or victor routes, RNAV specific 

information is printed in blue. [Figure 2-30] 

T270

70 

5000G 

*5400

6000G 

087 

67

268 088

NGOZI 

GRANT 

269

T270 

Waypoint 

Magnetic reference bearing 

T228 V333 

JES VAL BILLY TOMMY YATES 

333 332 4400 

10000 

7000G 

*6700 

10000 

8000G 

*6700 

10 10 49 40 109 

Figure 2-30. Joint Victor/RNAV airway. 

2-16 
 

 

 

 

N39'

111 

83 

34 

40 

27 

31 

92 

70 

142

244 

112

J26 

J26 

J96

133 

J87

21 

51 

J87 

J24

55 

J80

68 

002 

DRIVL 

SAAGS 

CORIM 

HUGIN 

FONIX 

KIDER

 BRAYMER

 111.2 BQS[L] 49 

NAPOLEON

 114.0 ANX[L] 87 

ROBINSON

 108.2 RBA[L] 19 

COLUMBIA 122.6 

115.9 SUM 106 

ST JOSEPH 

Rosaceach Mem 

[STJ] 

Sherman AAF 

(FLV) 

Lawrence Muni 

(LWC) 

TOPEKA 

Philip Billard Muni 

(TOP) 

Kansas City Intl 

(MCI) 

KANSAS CITY 

Charles B Wheeler 

Downtown 

(MKC) 

MOSBY 

Midwest National 

Air Control 

(GPH) 

Marshall Mem Muni 

(MHI) 

AGENT 

237 

266 66 257 

231 

145 

333

016 

057 

075

091° 

190° 

060° 

21 

35 

085 

080 

263 

260 

219

57 

38 

Figure 2-31. IFR en route high altitude chart. 

IFR En Route High Altitude Chart 

En route high altitude charts provide aeronautical 

information for navigation under IFR conditions at and 

above FL 180. [Figure 2-31] High altitude charts include 

the following information: 

•	 Jet route structure 

•	 RNAV Q-routes 

•	 VHF radio aids to navigation (frequency, ID, channel, 

geographic coordinates) 

•	 Selected airports 

•	 Reporting points 

•	 Navigation reference system (NRS) waypoints 

[Figure 2-32] 

Jet routes are depicted in black with a “J” identifier followed 

by the route number (e.g., “J12”) and are based on VOR or 

Figure 2-32. Navigation reference system (NRS) waypoints. W122° N40° 264 247

J189 

J501

RED BLUFF

115.7 RBA 104 

122.4 

H 

Chico Muni

(CIC) 

KO63E

KO60E

Redding Muni

(RDD) 

Red Bluff Muni

(RBL) 

Q5 

Q3 

Q1

135

203

MEA-22000 

MEA-24000D

1300-06002 

MEA CAP 1300-06002

MEA-24000D

1300-06002

MEA-26000D 

110 

134

Waypoint 

Waypoint 

162

144 

010

352

330 

RANCHO MURIETA 

N40°05.93'

W122°14.18' 

VORTAC NAVAIDs. [Figure 2-33] RNAV “Q” Route MEAs are 

shown when other than 18,000 feet. [Figure 2-34] MEAs 

for GNSS RNAV aircraft are identified with a “G” suffix. 

MEAs for DME/DME/IRU RNAV aircraft do not have a “G” 

suffix. All RNAV routes and associated data is charted in 

aeronautical blue and magnetic reference bearings are 

252

203

156 

159 

132 

(OFTEC) SAKES 

Green River Muni

(U34) 

Honksville 

MOAB

Camyonland’s Fld

(CNY) 

MEA-33000 

J196 

J196 

J80 

71 

055

073 254 

J80 

J28 

J28 

CEDAR CITY 111.2 

153 

50 

X

R-6413

Figure 2-33. High altitude jet routes. 

2-17 
 

 

 

Figure 2-34. MEAs on RNAV (Q) routes. 

Q5 

Q3 

Q1 

MEA-24000D

1300-06002

1300-06002

1300-06002 

MEA-24000D

MEA-26000D 

69

69 

69 

115.9 SUM 106 150 

149 

113 

ENVIE 

FINER 

HOMEG

OTTOO 

W123° 

150 

343 163

163

162 

343

343 

J12 Q7 

MEA - 27000 

MEA - 23000G 

300 

JointJet/RNAV Route 

Figure 2-35. Joint jet/RNAV routes. 

shown originating from a waypoint, fix/reporting point, or 

NAVAID. When joint Jet/RNAV routes are depicted, the route 

identification boxes are located adjacent to each other with 

the route charted in black. [Figure 2-35] With the exception 

of “Q” routes in the Gulf of Mexico, GNSS or DME/DME/IRU 

RNAV equipment is required along with radar monitoring 

capabilities. For aircraft that have DME/DME/IRU RNAV 

equipment, refer to the CS for specific DME information. 

VHF Airways 

Victor airways are a system of established routes that 

run along specified VOR radials, from one VOR station to 

another. The purpose is to make flight planning easier 

and they help ATC to organize and regulate the air traffic 

flow. Almost all commercial flights are routed along these 

airways but they are available for use by any pilot provided 

that the proper altitudes are employed. 

Victor Airway Navigation Procedures 

The procedure for getting established on a victor airway 

is to either fly directly to a nearby VOR or to intercept 

an airway radial along the route of flight. Once the pilot 

is established on an airway, it is important to follow the 

procedures and guidelines put in place to ensure air traffic 

separation and optimal safety on the airway. When using 

victor airways for navigation, procedures do not allow the 

pilot to jump from one VOR to another, but must navigate 

from one to the next by using the alternating outbound/ 

inbound procedure of linking VORs. For example, when 

departing from Zanesville VOR on V-214, the pilot selects 

the 090° radial with a FROM indication on the course 

deviation indicator (CDI) and should correct as necessary 

to continuously maintain track on the centerline of the 

airway. [Figure 2-36] The pilot should continue on this 

course until it is time to change over to the inbound course 

to the Bellaire VOR. 

LF/MF Airways 

The basic LF/MF airway width is 4.34 nautical miles (NM) 

on each side of the centerline; the width expands by five 

degrees when the distance from the facility providing 

course guidance is greater than 49.66 NM. [Figure 2-37] 

En Route Obstacle Clearance Areas 

All published routes in the NAS are based on specific 

obstacle clearance criteria. An understanding of en route 

obstacle clearance areas helps with SA and may help avoid 

controlled flight into terrain (CFIT). Obstacle clearance 

areas for the en route phase of flight are identified as 

primary, secondary, and turning areas. 

The primary and secondary area obstacle clearance 

criteria, airway and route widths, and the ATC separation 

procedures for en route segments are a function of 

safety and practicality in flight procedures. These flight 

procedures are dependent upon the pilot, the aircraft, and 

the navigation system being used, resulting in a total VOR 

system accuracy factor along with an associated probability 

2-18 
 

 

43 

50 29 

3000 

3000

17 

SABGE 

090° 

109 

334 

12 9 

12 

147 

347 

183 

LORES N40°

276 

15 

15

209 

22 2500 

3000

ZANDR 

MUNCE 

HISOM 5 

V214 

V117 

V117 

263 

272 

224

158 

330 

300

59-115 

Barnesville Brodfield

(6G5)

1312 4D L 

[2P7]

1187 L*28 

Cambridge Muni

(CDI)

799 43 L 

Zoneville Muni

(ZZV)

900 50 L

 ZANESVILLE

 111.4 ZZV 51 N42°34.15' W99°59.38' 

A 

CLEVELAND 

122.5 122.2 122.1R

 BELLAIRE

 117.1AIR 118 N40°31.00' W99°49.04' 

A 

CLEVELAND 

122.1R 

CLEVELAND Bolonl 120.4 257.975 

21 

33 

34 

17 

Figure 2-36. Zanesville VOR/Victor Airway 214. 

5° 

NBD 

4.34 NM 

49.66 NM 

5° NBD

5° 

5° 

Figure 2-37. LF/MR airway width. 

factor. The pilot/aircraft information component of these 

criteria includes pilot ability to track the radial and the flight 

track resulting from turns at various speeds and altitudes 

under different wind conditions. The navigation system 

information includes navigation facility radial alignment 

displacement, transmitter monitor tolerance, and receiver 

accuracy. All of these factors were considered during 

development of en route criteria. From this analysis, the 

computations resulted in a total system accuracy of ±4.5° 

95 percent of the time and ±6.7° 99 percent of the time. 

The 4.5° value became the basis for primary area obstacle 

clearance criteria, airway and route widths, and the ATC 

separation procedures. The 6.7° value provides secondary 

obstacle clearance area dimensions. 

Primary and Secondary En Route Obstacle 

Clearance Areas 

The primary obstacle clearance area has a protected width 

of 8 NM with 4 NM on each side of the centerline. The 

primary area has widths of route protection based upon 

system accuracy of a ±4.5° angle from the NAVAID. These 

4.5° lines extend out from the NAVAID and intersect the 

boundaries of the primary area at a point approximately 

51 NM from the NAVAID. Ideally, the 51 NM point is where 

pilots would change over from navigating away from the 

facility, to navigating toward the next facility, although this 

ideal is rarely achieved. [Figure 2-38] 

4.5° 

4.5° 

4.5° 

4.5° 

51 

51 

4 NM 

4 NM 

Primary obstacle clearance area 

V214 

Figure 2-38. Primary obstacle clearance area. 

2-19 
 

 

 

Primary en route obstacle clearance area 

1,000 feet above highest obstacle 

Figure 2-39. Non-mountainous obstacle clearance in the primary 

area. 

If the distance from the NAVAID to the change-over point 

(COP) is more than 51 NM, the outer boundary of the 

primary area extends beyond the 4 NM width along the 

4.5° line when the COP is at midpoint. This means the 

primary area, along with its obstacle clearance criteria, is 

extended out into what would have been the secondary 

area. Additional differences in the obstacle clearance area 

result in the case of the effect of an offset COP or dogleg 

segment. For protected en route areas, the minimum 

obstacle clearance in the primary area, not designated as 

mountainous under 14 CFR Part 95—IFR altitude, is 1,000 

feet over the highest obstacle. [Figure 2-39] The secondary 

obstacle clearance area extends along a line 2 NM on each 

side of the primary area. Navigation system accuracy in 

the secondary area has widths of route protection of a 

Figure 2-41. Primary and secondary obstacle clearance area. 

±6.7° angle from the NAVAID. These 6.7° lines intersect the 

outer boundaries of the secondary areas at the same point 

as primary lines, 51 NM from the NAVAID. If the distance 

from the NAVAID to the COP is more than 51 NM, the 

secondary area extends along the 6.7° line when the COP 

is at mid-point. [Figure 2-40] In all areas, mountainous and 

non-mountainous, obstacles that are located in secondary 

areas are considered as obstacles to air navigation if they 

extend above the secondary obstacle clearance plane. 

This plane begins at a point 500 feet above the obstacles 

(natural or man-made) upon which the primary obstacle 

clearance area is based, and slants upward at an angle that 

causes it to intersect the outer edge of the secondary area 

at a point 500 feet higher. [Figure 2-41] 

Changeover Points 

When flying airways, pilots normally change frequencies 

midway between NAVAIDs, although there are times 

when this is not practical. If the navigation signals cannot 

be received from the second VOR at the midpoint of the 

route, a COP is depicted and shows the distance in NM to 

each NAVAID. [Figure 2-42] COPs indicate the point where a 

frequency change is necessary to receive course guidance 

from the facility ahead of the aircraft instead of the one 

6.7° 

6.7° 

6.7° 

6.7° 

51 

51 

4 NM 

4 NM 

2 NM 

Secondary obstacle clearance area 

V214 

2 NM 

Figure 2-40. Secondary obstacle clearance area. 

2-20 
 

13,000 ft 

13,000 

22 

45 

V344 

Figure 2-42. Changeover points. 

behind. These COPs divide an airway or route segment and 

ensure continuous reception of navigation signals at the 

prescribed minimum en route IFR altitude. They also ensure 

that other aircraft operating within the same portion of 

an airway or route segment receive consistent azimuth 

signals from the same navigation facilities regardless of 

the direction of flight. 

Where signal coverage from two VORs overlaps at the MEA, 

the COP normally is designated at the midpoint. Where 

radio frequency interference or other navigation signal 

problems exist, the COP is placed at the optimum location, 

taking into consideration the signal strength, alignment 

error, or any other known condition that affects reception. 

The COP has an effect on the primary and secondary 

obstacle clearance areas. On long airway or route segments, 

if the distance between two facilities is over 102 NM and the 

COP is placed at the midpoint, the system accuracy lines 

extend beyond the minimum widths of 8 and 12 NM, and a 

flare or spreading outward results at the COP. [Figure 2-43] 

Offset COP and dogleg segments on airways or routes can 

also result in a flare at the COP. 

Direct Route Flights 

Direct route flights are flights that are not flown on the 

radials or courses of established airways or routes. Direct 

route flights must be defined by indicating the radio fixes 

over which the flight passes. Fixes selected to define the 

route should be those over which the position of the aircraft 

can be accurately determined. Such fixes automatically 

become compulsory reporting points for the flight, unless 

advised otherwise by ATC. Only those NAVAIDs established 

Figure 2-43. Changeover point effect on long airway or route segment. 

4.5° 

6.7° 4.5° 

70 6.7°

70 

4 NM 

4 NM 

Secondary areas 

Primary areas 

V214 

2 NM 

2 NM 

Flare 

Flare 

2-21 
NOT FOR NAVIGATION

T FOR NAVIGATIO

Figure 2-44. Direct route navigation. 

for use in a particular structure (i.e., in the low or high 

structures) may be used to define the en route phase of a 

direct flight within that altitude structure. 

Figure 2-44 shows a straight line on a magnetic course 

from SCRAN intersection of 270° direct to the Fort Smith 

Regional Airport in Arkansas that passes just north of 

restricted areas R-2401A and B and R-2402. Since the airport 

and the restricted areas are precisely plotted, there is an 

assurance that you will stay north of the restricted areas. 

From a practical standpoint, it might be better to fly direct 

to the Wizer NDB. This route goes even further north of the 

restricted areas and places you over the final approach fix 

to Runway 25 at Fort Smith. 

The azimuth feature of VOR aids and the azimuth and 

distance (DME) features of VORTAC and TACAN aids are 

assigned certain frequency protected areas of airspace that 

are intended for application to established airway and route 

use and to provide guidance for planning flights outside 

of established airways or routes. These areas of airspace 

are expressed in terms of cylindrical service volumes of 

specified dimensions called class limits or categories. 

An operational service volume has been established 

for each class in which adequate signal coverage and 

frequency protection can be assured. To facilitate use 

of VOR, VORTAC, or TACAN aids, consistent with their 

operational service volume limits, pilot use of such aids 

for defining a direct route of flight in controlled airspace 

should not exceed the following: 

1.	 Operations above FL 450—use NAVAIDs not more 

than 200 NM apart. These aids are depicted on en 

route high altitude charts. 

2.	 Operation off established routes from 18,000 feet 

MSL to FL 450—use NAVAIDs not more than 260 

NM apart. These aids are depicted on en route high 

altitude charts. 

3.	 Operation off established airways below 18,000 feet 

MSL—use NAVAIDs not more than 80 NM apart. 

These aids are depicted on en route low altitude charts. 

4.	 Operation off established airways between 14,500 

2-22 
 

 

 

feet MSL and 17,999 feet MSL in the conterminous 

United States—(H) facilities not more than 200 NM 

apart may be used. 

Increasing use of self-contained airborne navigational 

systems that do not rely on the VOR/VORTAC/TACAN 

system has resulted in pilot requests for direct routes that 

exceed NAVAID service volume limits. These direct route 

requests are approved only in a radar environment with 

approval based on pilot responsibility for navigation on the 

authorized direct route. Radar flight following is provided 

by ATC for ATC purposes. At times, ATC initiates a direct 

route in a radar environment that exceeds NAVAID service 

volume limits. In such cases, ATC provides radar monitoring 

and navigational assistance as necessary. 

When filing for a direct route flight, airway or jet route 

numbers, appropriate to the stratum in which operation 

is conducted, may also be included to describe portions 

of the route to be flown. The following is an example of 

how a direct route flight would be written. 

MDW V262 BDF V10 BRL STJ SLN GCK 

Spelled out: from Chicago Midway Airport via Victor 

262 to Bradford, Victor 10 to Burlington, Iowa, direct St. 

Joseph, Missouri, direct Salina, Kansas, direct Garden 

City, Kansas. 

Note: When route of flight is described by radio fixes, 

the pilot is expected to fly a direct course between the 

points named. 

Pilots should keep in mind that they are responsible 

for adhering to obstruction clearance requirements 

on those segments of direct routes that are outside of 

controlled airspace. The MEAs and other altitudes shown 

on low altitude IFR en route charts pertain to those route 

segments within controlled airspace, and those altitudes 

may not meet obstruction clearance criteria when 

operating off those routes. 

Published RNAV Routes 

Published RNAV routes are fixed, permanent routes that 

can be flight planned and flown by aircraft with RNAV 

capability. These are being expanded worldwide as 

new RNAV routes are developed, and existing charted, 

conventional routes are being designated for RNAV use. It 

is important to be alert to the rapidly changing application 

of RNAV techniques being applied to conventional en 

route airways. Published RNAV routes may potentially be 

found on any en route chart. The published RNAV route 

designation may be obvious, or, on the other hand, RNAV 

route designations may be less obvious, as in the case 

where a published route shares a common flight track with 

a conventional airway. 

Note: The use of RNAV is dynamic and rapidly changing; 

therefore, en route charts are continuously being updated 

for information changes, and you may find some differences 

between charts. 

Basic designators for air traffic service (ATS) routes and 

their use in voice communications have been established. 

One of the main purposes of a system of route designators 

is to allow both pilots and ATC to make unambiguous 

reference to RNAV airways and routes. Basic designators 

for ATS routes consist of a maximum of five, and in no 

case to exceed six, alpha/numeric characters in order to be 

usable by both ground and airborne automation systems. 

The designator indicates the type of the route, such as 

high/low altitude, specific airborne navigation equipment 

requirements, such as RNAV, and the aircraft type using the 

route primarily and exclusively. The basic route designator 

consists of one or two letter(s) followed by a number from 

1 to 999. 

Composition of Designators 

The prefix letters that pertain specifically to RNAV 

designations are included in the following list: 

1.	 The basic designator consists of one letter of the 

alphabet followed by a number from 1 to 999. The 

letters may be: 

a. A, B, G, R—for routes that form part of the 

regional networks of ATS route and are not 

RNAV routes; 

b. L, M, N, P—for RNAV routes that form part of 

the regional networks of ATS routes; 

c. H, J, V, W—for routes that do not form part of 

the regional networks of ATS routes and are not 

RNAV routes; 

d. Q, T, Y, Z—for RNAV routes that do not form 

part of the regional networks of ATS routes. 

2.	 Where applicable, one supplementary letter must be 

added as a prefix to the basic designator as follows: 

a.	 K—to indicate a low level route established for 

use primarily by helicopters; 

b.	 U—to indicate that the route or portion thereof 

is established in the upper airspace; 

c.	 S—to indicate a route established exclusively for 

use by supersonic aircraft during acceleration/ 

deceleration and while in supersonic flight. 

3.	 Where applicable, a supplementary letter may be 

added after the basic designator of the ATS route as 

a suffix as follows: 

2-23 
Figure 2-45. Published RNAV jet routes. 

NOT FOR NAVIGATION

N60°53.97 ́ W 151°2163 ́ 

114.3 ANC 221.3°-37.0 

AMOTT 

280 

MEA-28000 

J888R 

J996R 

J804R

61.2 

61° 

246 237

226° 

AMOTT 

37 

22

10346 

a. F—to indicate that on the route or portion thereof 

advisory service only is provided; 

b. G—to indicate that on the route or portion thereof 

flight information services only is provided; 

c. Y—for RNP 1 routes at and above FL 200 to 

indicate that all turns on the route between 30° 

and 90° must be made within the tolerance of a 

tangential arc between the straight leg segments 

defined with a radius of 22.5 NM; 

d. Z—for RNP 1 routes at and below FL 190 to 

indicate that all turns on the route between 30° 

and 90° should be made within the tolerance 

of a tangential arc between the straight leg 

segments defined with a radius of 15 NM. 

Note: RNAV Q-routes require en route RNAV 2, corresponding 

NAV/E2 code and PBN/C1-C4 based on navigation system 

update source. 

Use of Designators in Communications 

In voice communications, the basic letter of a designator 

should be spoken in accordance with the International Civil 

Aviation Organization (ICAO) spelling alphabet. Where the 

prefixes K, U, or S, previously mentioned, are used in voice 

communications, they should be pronounced as: 

K—Kopter 

U—Upper, as in the English language 

S—Supersonic 

Where suffixes F, G, Y or Z specified in above, are used, the 

flight crew should not be required to use them in voice 

communications. Below is an example of how the letters 

and numbers are spoken. 

A11—Alpha Eleven 

UR5—Upper Romeo Five 

KB34—Kopter Bravo Thirty Four 

UW456—Upper Whiskey Four Fifty Six 

2-24 
 

 

 

 

The en route chart excerpt depicts three published RNAV jet 

routes: J804R, J888R, and J996R. [Figure 2-45] The R suffix 

is a supplementary route designator denoting an RNAV 

route. The overlapping symbols for the AMOTT intersection 

and waypoint indicate that AMOTT can be identified by 

conventional navigation or by latitude and longitude 

coordinates. Although coordinates were originally included 

for aircraft equipped with an inertial navigation system 

(INS), they are now a good way to cross check between 

the coordinates on the chart and in the flight management 

system (FMS) or global positioning system (GPS) databases 

to ensure you are tracking on your intended en route 

course. The AMOTT RNAV waypoint includes bearing and 

distance from the Anchorage VORTAC. 

Random RNAV Routes 

Random RNAV routes are direct routes that are based on 

RNAV capability between waypoints defined in terms of 

latitude or longitude coordinates, degree-distance fixes, 

or offsets from established routes or airways at a specified 

distance and direction. Radar monitoring by ATC is required 

on all random RNAV routes. Random RNAV routes can 

only be approved in a radar environment. Factors that 

are considered by ATC when approving random RNAV 

routes include the capability to provide radar monitoring 

and compatibility with traffic volume and flow. ATC radar 

monitor each flight; however, navigation on the random 

RNAV route is the responsibility of the pilot. 

Pilots flying aircraft that are equipped with approved area 

navigation equipment may file for RNAV routes throughout 

the NAS and may be filed for in accordance with the 

following procedures: 

1.	 File airport-to-airport flight plans. 

2.	 File the appropriate RNAV capability certification 

suffix in the flight plan. 

3.	 Plan the random route portion of the flight plan 

to begin and end over appropriate arrival and 

departure transition fixes or appropriate NAVAIDs 

for the altitude stratum within which the flight is 

conducted. The use of normal preferred DPs and 

STAR, where established, is recommended. 

4.	 File route structure transitions to and from the 

random route portion of the flight. 

5.	 Define the random route by waypoints. File route 

description waypoints by using degree distance fixes 

based on navigational aids that are appropriate for 

the altitude stratum. 

6.	 File a minimum of one route description waypoint 

for each ARTCC through whose area the random 

route is flown. These waypoints must be located 

within 200 NM of the preceding center’s boundary. 

7.	 File an additional route description waypoint for 

each turnpoint in the route. 

8.	 Plan additional route description waypoints as 

required to ensure accurate navigation via the filed 

route of flight. Navigation is the pilot’s responsibility 

unless ATC assistance is requested. 

9.	 Plan the route of flight so as to avoid prohibited and 

restricted airspace by 3 NM unless permission has 

been obtained to operate in that airspace and the 

appropriate ATC facilities are advised. 

Note: To be approved for use in the NAS, RNAV equipment 

must meet the appropriate system availability, accuracy, 

and airworthiness standards. For additional guidance 

on equipment requirements, see Advisory Circular (AC) 

20-138C, Airworthiness Approval of Positioning and 

Navigation Systems. For airborne navigation database, 

see AC 90-105, Approval Guidance for RNP Operations 

and Barometric Vertical Navigation in the U.S. National 

Airspace System. 

Pilots flying aircraft that are equipped with latitude/ 

longitude coordinate navigation capability, independent 

of VOR/ TACAN references, may file for random RNAV routes 

at and above FL 390 within the conterminous United States 

using the following procedures: 

1.	 File airport-to-airport flight plans prior to departure. 

2.	 File the appropriate RNAV capability certification 

suffix in the flight plan. 

3.	 Plan the random route portion of the flight to 

begin and end over published departure/arrival 

transition fixes or appropriate NAVAIDs for airports 

without published transition procedures. The use of 

preferred departure and arrival routes, such as DP 

and STAR where established, is recommended. 

4.	 Plan the route of flight so as to avoid prohibited and 

restricted airspace by 3 NM unless permission has 

been obtained to operate in that airspace and the 

appropriate ATC facility is advised. 

5.	 Define the route of flight after the departure fix, 

including each intermediate fix (turnpoint) and 

the arrival fix for the destination airport in terms 

of latitude/longitude coordinates plotted to the 

nearest minute or in terms of Navigation Reference 

System (NRS) waypoints. For latitude/longitude 

filing, the arrival fix must be identified by both the 

latitude/ longitude coordinates and a fix identifier 

as shown in the example below. 

MIA1 SRQ2 3407/106153 3407/11546 TNP4 LAX5 

1Departure airport 

2-25 
 

 

2Departure fix 

3Intermediate fix (turning point) 

4Arrival fix 

5Destination airport 

Or: 

ORD1 IOW2 KP49G3 KD34U4 KL16O5 OAL6 MOD27 

SFO8 

1Departure airport 

2Transition fix (pitch point) 

3Minneapolis ARTCC waypoint 

4Denver ARTCC waypoint 

5Los Angeles ARTCC waypoint (catch point) 

6Transition fix 

7Arrival 

8Destination airport 

6.	 Record latitude/longitude coordinates by four 

figures describing latitude in degrees and minutes 

followed by a solidus and five figures describing 

longitude in degrees and minutes. 

7.	 File at FL 390 or above for the random RNAV portion 

of the flight. 

8.	 Fly all routes/route segments on Great Circle tracks. 

9.	 Make any in-flight requests for random RNAV 

clearances or route amendments to an en route ATC 

facility. 

Figure 2-46. Excerpt of authorized areas of en route operation. 

SAMPLE NOT FOR 

ACTUAL USE

The 48 contiguous United 

States and the District of 

Columbia 

Canada, excluding Canadian 

MNPS airspace and the areas 

of magnetic unreliability as 

established in the Canadian 

AIP 

SPECIAL REQUIREMENTS: 

Note 1 - B-737 Class II navigation operations with a single longrange system is authorized only within this area of en route 

operation. 

Note 3 - Only B-747 and DC-10 operations authorized in these 

areas. 

Note 1 

Note 3 

Authorized areas of 

en route operation 

Limitations, provisions,

and reference paragraphs 

Off-Airway Routes 

14 CFR Part 95 prescribes altitudes governing the operation 

of aircraft under IFR on Federal airways, jet routes, RNAV low 

or high altitude routes, and other direct routes for which a 

MEA is designated. In addition, it designates mountainous 

areas and COPs. Off-airway routes are established in the 

same manner and in accordance with the same criteria 

as airways and jet routes. If a pilot flies for a scheduled air 

carrier or operator for compensation or hire, any requests for 

the establishment of off-airway routes are initiated by the 

company through the principal operations inspector (POI) 

who works directly with the company and coordinates FAA 

approval. Air carrier authorized routes should be contained 

in the company’s Operations Specifications (OpSpecs) under 

the auspices of the air carrier operating certificate. [Figure 

2-46] 

Off-airway routes predicated on public navigation 

facilities and wholly contained within controlled airspace 

are published as direct Part 95 routes. Off-airway routes 

predicated on privately owned navigation facilities or 

not contained wholly within controlled airspace are 

published as off-airway non-Part 95 routes. In evaluating 

the adequacy of off-airway routes, the following items are 

considered: the type of aircraft and navigation systems 

used; proximity to military bases, training areas, low level 

military routes; and the adequacy of communications 

along the route. 

Commercial operators planning to fly off-airway routes 

should have specific instructions in the company’s 

OpSpecs that address en route limitations and provisions 

regarding en route authorizations to use the GPS or other 

RNAV systems in the NAS. The company’s manuals and 

checklists should include practices and procedures for 

long-range navigation and training on the use of long 

range navigation equipment. Minimum equipment lists 

(MELs) and maintenance programs must address the long 

range navigation equipment. Examples of other selected 

areas requiring specialized en route authorization include 

the following: 

•	 Class I navigation in the United States Class A 

airspace using area of long range navigation system. 

•	 Class II navigation using multiple long range 

navigation systems. 

•	 Operations in central East Pacific airspace. 

•	 North Pacific operations. 

•	 Operations within North Atlantic (NAT) minimum 

navigation performance specifications (MNPS) 

airspace. 

2-26 
 

 

 

 

•	 Operations in areas of magnetic unreliability. 

•	 North Atlantic operation (NAT/OPS) with two engine 

aircraft under 14 CFR Part 121. 

•	 Extended range operations (ER-OPS) with two 

engine aircraft under 14 CFR Part 121. 

•	 Special fuel reserves in international operations. 

•	 Planned in-flight re-dispatch or re-release en route. 

•	 Extended over water operations using a single longrange communication system. 

•	 Operations in reduced vertical separation minimum 

(RVSM) airspace. 

Off-Route Obstruction Clearance Altitude 

An off-route obstruction clearance altitude (OROCA) is 

an off-route altitude that provides obstruction clearance 

with a 1,000-foot buffer in non-mountainous terrain areas 

and a 2,000-foot buffer in designated mountainous areas 

within the United States. This altitude may not provide 

signal coverage from ground-based NAVAIDs, ATC radar, 

or communications coverage. OROCAs are intended 

primarily as a pilot tool for emergencies and SA. OROCAs 

depicted on en route charts do not provide the pilot with 

an acceptable altitude for terrain and obstruction clearance 

for the purposes of off-route, random RNAV direct flights 

in either controlled or uncontrolled airspace. OROCAs 

are not subject to the same scrutiny as MEAs, minimum 

vectoring altitude (MVAs), MOCAs, and other minimum IFR 

altitudes. Since they do not undergo the same obstruction 

evaluation, airport airspace analysis procedures, or 

flight inspection, they cannot provide the same level of 

confidence as the other minimum IFR altitudes. 

When departing an airport VFR intending to or needing to 

obtain an IFR clearance en route, you must be aware of the 

position of your aircraft relative to terrain and obstructions. 

When accepting a clearance below the MEA, MIA, MVA, 

or the OROCA, you are responsible for your own terrain/ 

obstruction clearance until reaching the MEA, MIA, or MVA. 

If unable to visually maintain terrain/obstruction clearance, 

pilots should advise ATC and state intentions of the flight. 

[Figure 2-47] 

NOT FOR NAVIGATION

Figure 2-47. Off-route obstacle clearance altitude. 

2-27 
Figure 2-48. Random RNAV route. 

For all random RNAV flights, there needs to be at least one 

waypoint in each ARTCC area through which you intend 

to fly. One of the biggest problems in creating an RNAV 

direct route is determining if the route goes through special 

use airspace. For most direct routes, the chances of going 

through prohibited, restricted, or special use airspace 

are good. In the United States, all direct routes should be 

planned to avoid prohibited or restricted airspace by at 

least 3 NM. If a bend in a direct route is required to avoid 

special use airspace, the turning point needs to be part 

of the flight plan. Two of the most prominent long range 

navigation systems today include FMS with integrated GPS 

and stand-alone GPS. The following example is a simplified 

overview showing how the RNAV systems might be used 

to fly a random RNAV route. 

Shown in Figure 2-48, the aircraft is northeast of Tuba City 

VORTAC at FL 200 using RNAV (showing both GPS and 

FMS), RNAV direct on a southwesterly heading to Lindbergh 

Regional Airport in Winslow. As the pilot is monitoring his 

or her position and cross-checking the avionics against the 

high altitude en route chart, he or she receives a company 

2-28 
 

 

 

message instructing to divert to Las Vegas, requiring a 

change in the flight plan as highlighted on the depicted 

chart excerpt. 

During the flight deck review of the high and low altitude 

en route charts, the pilot determines that the best course 

of action is to fly direct to the MIRAJ waypoint, 28 DME 

northeast of the Las Vegas VORTAC on the 045° radial. This 

places the aircraft 193 NM out on a 259° magnetic course 

inbound, and may help to avoid diverting north, allowing to 

bypass the more distant originating and intermediate fixes 

feeding into Las Vegas. The pilot requests an RNAV random 

route clearance direct MIRAJ to expedite the flight. Denver 

Center comes back with the following amended flight plan 

and initial clearance into Las Vegas: 

“Marathon five sixty four, turn right heading two six zero, 

descend and maintain one six thousand, cleared present 

position direct MIRAJ.” 

The latitude and longitude coordinates of the aircraft’s 

present position on the high altitude chart is N36 19.10 

and W110 40.24 as the course is changed. Notice the GPS 

moving map (upper left), the FMS control display unit 

(below the GPS), and FMS map mode navigation displays 

(to the right of the GPS) as the flight is rerouted to Las Vegas. 

For SA, the pilot makes note that the altitude is well above 

any of the OROCAs on the direct route as the flight arrives 

in the Las Vegas area using the low altitude chart. 

Monitoring of Navigation Facilities 

VOR, VORTAC, and instrument landing system (ILS) facilities, 

as well as most NDBs and marker beacons installed by the 

FAA, are provided with an internal monitoring feature. 

Internal monitoring is provided at the facility through 

the use of equipment that causes a facility shutdown if 

performance deteriorates below established tolerances. 

A remote status indicator also may be provided through 

the use of a signal-sampling receiver, microwave link, or 

telephone circuit. Older FAA NDBs and some non-Federal 

NDBs do not have the internal feature, and monitoring is 

accomplished by manually checking the operation at least 

once each hour. FAA facilities, such as automated flight 

service stations (AFSSs) and ARTCCs/sectors, are usually 

the control point for NAVAID facility status. Pilots can query 

the appropriate FAA facility if they have questions in flight 

regarding NAVAID status, in addition to checking NOTAMs 

prior to flight, since NAVAIDs and associated monitoring 

equipment are continuously changing. 

Navigational Gaps 

A navigational course guidance gap, referred to as an 

MEA gap, describes a distance along an airway or route 

segment where a gap in navigational signal coverage 

exists. The navigational gap may not exceed a specific 

distance that varies directly with altitude, from 0 NM at sea 

level to 65 NM at 45,000 feet MSL and not more than one 

gap may exist in the airspace structure for the airway or 

route segment. Additionally, a gap usually does not occur 

at any airway or route turning point. To help ensure the 

maximum amount of continuous positive course guidance 

available when flying, there are established en route criteria 

for both straight and turning segments. Where large gaps 

exist that require altitude changes, MEA “steps” may be 

established at increments of not less than 2,000 feet below 

18,000 feet MSL, or not less than 4,000 feet at 18,000 MSL 

and above, provided that a total gap does not exist for the 

entire segment within the airspace structure. MEA steps are 

limited to one step between any two facilities to eliminate 

continuous or repeated changes of altitude in problem areas. 

The allowable navigational gaps pilots can expect to see 

are determined, in part, by reference to the graph depicted 

in Figure 2-49. Notice the en route chart excerpt depicting 

that the MEA is established with a gap in navigation signal 

coverage northwest of the Carbon VOR/DME on V134. At 

the MEA of 13,000, the allowable navigation course guidance 

gap is approximately 18.5 NM, as depicted in Figure 2-49. 

The navigation gap area is not identified on the chart 

by distances from the navigation facilities. Proper flight 

planning will help pilots prepare for MEA gaps by insuring 

that appropriate maps are available as they may need 

to dead reckon through the gap. Calculating the ground 

track (with adjustments for winds) before and after the gap 

will also help to stay on course when navigational course 

guidance is not available. 

NAVAID Accuracy Check 

The CFRs and good judgment dictate that the equipment 

of aircraft flying under IFR be within a specified tolerance 

before taking off. When approved procedures are available, 

they should be used for all equipment inspections. 

VOR Accuracy 

VOR accuracy can be checked by using any of the following 

methods: VOR test facility signal (VOT), VOR checkpoint 

signs, dual VOR check, or airborne VOR check. 

VOT 

The VOT is an approved test signal and is located on an 

airport. This enables the pilot to check the VOR accuracy 

from the flight deck before takeoff. Listed below are the 

steps used for a VOT: 

1.	 Tune the VOR receiver to the VOT frequency. VOT 

frequencies can be found in the CS. [Figure 2-50] 

These frequencies are coded with a series of Morse 

code dots or a continuous 1020-cycle tone. 

2-29 
 

Sample: Enter with MEA of 13,000 feet. Read allowable gap 18.5 NM. 

60 

55 

50 

45 

40 

35 

30 

25 

20 

15 

10 

5 

0 

5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 

Allowable navigation course guidance gap (NM) 

NOT FOR

 NAVIGATION

MEA of airway or route segment (thousands of feet) 

Figure 2-49. Navigational course guidance gaps. 

VOR test facilities (VOT) 

Facility Name .............................. Type VOT 

(Airport Name) ...........Frequency Facility Remarks 

Bradlay Intl .................... 111.40 G 

Bridgeport ..................... 109.25 G 

Groton ........................... 110.25 G 

Hartford ......................... 108.20 G 

Figure 2-50. VOR test facilities (VOT) frequencies. 

Figure 2-51. VOR checkpoint signs. 

VOR 116.4 

147° 4.1 NM 

DME and VOR check radial 

2.	 On the VOR, set the course selector to 0° and the 

track bar (TB) indicator should read center. The TOFROM indicator should read FROM. 

3.	 Set the course selector to 180° and the TO-FROM 

indicator should read TO and the TB should then be 

centered. 

Note: Determining the exact error in the receiver is done 

by turning the track selector until the TB is centered and 

noting the degrees difference between 180° or 0°. The 

maximum bearing error with the VOT system check is plus 

or minus 4° and apparent errors greater than 4° indicate 

that the VOR receiver is beyond acceptable tolerance. 

VOR Checkpoint Signs 

Many aerodromes have VOR checkpoint signs that are 

located beside the taxiways. [Figure 2-51] These signs 

indicate the exact point on the aerodrome that there is 

sufficient signal strength from a VOR to check the aircraft’s 

2-30 
 

 

VOR receiver against the radial designated on the sign. 

Listed below are the steps to use at a VOR checkpoint: 

1.	 Tune the proper VOR frequency. 

2.	 Identify the VOR frequency. V

3.	 Set the published radial on the course deviation fl

indicator (CDI). r

4.	 Confirm that the TB is centered. t

o 5.	 Check the needle sensitivity by changing the 

omnibearing select (OBS) 10° each way. 

6.	 Set the reciprocal of the radial and check the TO T FROM flag change. 

n

7.	 The maximum permissible difference between f

aircraft equipment and the designated radial is 4° i

and 0.5 NM of the posted distance. s

­

Dual VOR Check 

If a VOT or VOR checkpoint is not available and the aircraft is 

equipped with dual VORs, the equipment may be checked 

against one another by tuning both sets to the VOR facility 

at the same time and noting the indicated bearings to that 

station. [Figure 2-52] A difference greater than 4° between 

the two VORs indicates that one of the receivers may be 

out of tolerance. 

Airborne VOR Check 

OR equipment can also be checked for accuracy while in 

ight by flying over a fix or landmark located on a published 

adial and noting the indicated radial. Variances of more 

han 6° from the published radial should be considered out 

f tolerance and not be used for IFR navigation. 

NDB Accuracy Check 

he pilot must identify an NDB before using it for 

avigation, and continuously monitor it while using it 

or an instrument approach. The lack of an IDENT may 

ndicate that the NDB is out of service, even though it may 

till be transmitting (for instance for maintenance or test 

purposes). If an incorrect IDENT is heard, then the NDB 

should not be used. 

RNAV Accuracy Check 

RNAV accuracy checks may differ depending on the 

different type of equipment and manufacturer. When 

available, all written procedures should be followed. 

Figure 2-52. Instrument panel with dual VORs. 

2-31 
 

 

 

 

Below is a list of generic checks that should be used when 

checking the accuracy of the system prior to flight. 

1.	 System initialization—pilots should confirm that 

the navigation database is current and verify that the 

aircrafts present position has been entered correctly. 

2.	 Active flight plan check—the active flight plan 

should be checked by comparing the aeronautical 

charts, departure and arrival procedures, and other 

applicable documents with the map display. 

Figure 2-53. Fly-by and fly-over waypoints. 

Fly-by waypoint 

Fly-over waypoint 

Alpha 

Bravo 

Bravo 

Alpha 

3.	 Prior to takeoff—ensure that the RNAV system is 

available. If possible, check to see that the system 

is updating when aircraft position is changing. 

Note: While in flight, continue to verify system accuracy 

by displaying bearing/range to a VOR/DME on the RNAV 

system and compare it to the actual RMI reading of that 

particular NAVAID. 

Waypoints 

Waypoints are predetermined geographical locations that 

are defined in terms of latitude/longitude coordinates or 

fixes, used to define an RNAV route or the flight path of 

an aircraft employing RNAV. Waypoints may be a simple 

named point in space or may be associated with existing 

NAVAIDs, intersections, or fixes. A waypoint is most often 

used to indicate a change in direction, speed, or altitude 

along the desired path. Aviation RNAV procedures make 

use of both fly-over and fly-by waypoints. A fly-over 

waypoint is a waypoint that must be crossed vertically by 

an aircraft. A fly-by waypoint is a waypoint that marks the 

intersection of two straight paths, with the transition from 

one path to another being made by the aircraft using a 

precisely calculated turn that flies by but does not vertically 

cross the waypoint. [Figure 2-53] 

User-Defined Waypoints 

Pilots typically create user-defined waypoints for use in 

their own random RNAV direct navigation. They are newly 

established, unpublished airspace fixes that are designated 

geographic locations/positions that help provide positive 

course guidance for navigation and a means of checking 

progress on a flight. They may or may not be actually 

plotted by the pilot on en route charts, but would normally 

be communicated to ATC in terms of bearing and distance 

or latitude/longitude. An example of user-defined 

waypoints typically includes those generated by various 

means including keyboard input, and even electronic map 

mode functions used to establish waypoints with a cursor 

on the display. 

Another example is an offset phantom waypoint, which is 

a point-in-space formed by a bearing and distance from 

NAVAIDs, such as VORTACs and tactical air navigation 

(TACAN) stations, using a variety of navigation systems. 

When specifying unpublished waypoints in a flight plan, 

they can be communicated using the frequency/bearing/ 

distance format or latitude and longitude, and they 

automatically become compulsory reporting points unless 

otherwise advised by ATC. All aircraft with latitude and 

longitude navigation systems flying above FL 390 must use 

latitude and longitude to define turning points. 

Floating Waypoints 

Floating waypoints, or reporting points, represent 

airspace fixes at a point in space not directly associated 

with a conventional airway. In many cases, they may be 

established for such purposes as ATC metering fixes, 

holding points, RNAV-direct routing, gateway waypoints, 

STAR origination points leaving the en route structure, 

and SID terminating points joining the en route structure. 

In the top example of Figure 2-54, a low altitude en route 

chart depicts three floating waypoints that have been 

highlighted: SCORR, FILUP, and CHOOT. Notice that 

waypoints are named with five-letter identifiers that are 

unique and pronounceable. Pilots must be careful of 

similar waypoint names. Notice on the high altitude en 

route chart excerpt in the bottom example, the similar 

sounding and spelled floating waypoint named SCOOR, 

rather than SCORR. This emphasizes the importance 

of correctly entering waypoints into database-driven 

navigation systems. One waypoint character incorrectly 

entered into your navigation system could adversely affect 

your flight. The SCOOR floating reporting point also is 

2-32 
 

 

Figure 2-54. Floating waypoints. 

depicted on a Severe Weather Avoidance Plan (SWAP) en 

route chart. These waypoints and SWAP routes assist pilots 

and controllers when severe weather affects the East Coast. 

Computer Navigation Performance 

An integral part of RNAV using en route charts typically 

involves the use of airborne navigation databases. 

Because GPS receivers are basically “to-to” navigators, 

they must always be navigating to a defined point. On 

overlay approaches, if no pronounceable five-character 

name is published for an approach waypoint or fix, it has 

been given a database identifier consisting of letters and 

numbers. These points appear in the list of waypoints in the 

approach procedure database, but may not appear on the 

approach chart. A point used for the purpose of defining 

the navigation track for an airborne computer system (i.e., 

GPS or FMS) is called a Computer Navigation Fix (CNF). CNFs 

include unnamed DME fixes, beginning and ending points 

of DME arcs, and sensor final approach fixes (FAFs) on some 

GPS overlay approaches. 

To aid in the approach chart/database correlation process, 

the FAA has begun a program to assign five-letter names 

to CNFs and to chart CNFs on various National Oceanic 

Service aeronautical products. [Figure 2-55] These CNFs 

are not to be used for any ATC application, such as holding 

for which the fix has not already been assessed. CNFs are 

charted to distinguish them from conventional reporting 

points, fixes, intersections, and waypoints. A CNF name is 

enclosed in parenthesis, e.g., (MABEE) and is placed next 

to the CNF it defines. If the CNF is not at an existing point 

defined by means such as crossing radials or radial/DME, 

the point is indicated by an X. The CNF name is not used in 

filing a flight plan or in aircraft/ATC communications. Use 

current phraseology (e.g., facility name, radial, distance) to 

describe these fixes. 

2-33 
NOT FOR NAVIGATION

Figure 2-55. Computer navigation fix. 

Many of the RNAV systems available today make it all 

too easy to forget that en route charts are still required 

and necessary for flight. As important as databases are, 

they really are onboard the aircraft to provide navigation 

guidance and situational awareness (SA); they are not 

intended as a substitute for paper charts. When flying 

with GPS, FMS, or planning a flight with a computer, it is 

critical to understand the limitations of the system you are 

using, for example, incomplete information, unloadable 

procedures, complex procedures, and database storage 

limitations. 

Required Navigation Performance 

Required navigation performance (RNP) is RNAV with 

onboard navigation monitoring and alerting. RNP is also 

a statement of navigation performance necessary for 

operation within a defined airspace. A critical component 

of RNP is the ability of the aircraft navigation system to 

monitor its achieved navigation performance, and to 

identify for the pilot whether the operational requirement 

is, or is not being met during an operation. This onboard 

performance monitoring and alerting capability; 

therefore, allows a lessened reliance on ATC intervention 

(via radar monitoring, automatic dependent surveillancebroadcast (ADS-B), multilateration, communications), 

and/or route separation to achieve the overall safety of 

the operation. RNP capability of the aircraft is a major 

component in determining the separation criteria to 

ensure that the overall containment of the operation is 

met. 

The RNP capability of an aircraft varies depending upon 

the aircraft equipment and the navigation infrastructure. 

For example, an aircraft may be equipped and certified 

for RNP 1.0, but may not be capable of RNP 1.0 operations 

due to limited NAVAID coverage. 

0.1 to 1.0 

0.3 to 1.0 

1 

2 

RNP AR Approach Segments 

RNP Approach Segments 

Terminal and En Route 

En Route 

0.1 to 1.0 

0.3 to 1.0 

1.0 

2.0 

RNP Level Typical Application Primary Route Width (NM) - Centerline to Boundary 

Figure 2-56. U.S. standard RNP levels. 

2-34 
 

RNP Levels 

An RNP level or type is applicable to a selected airspace, 

route, or procedure. As defined in the Pilot/Controller 

Glossary, the RNP level or type is a value typically expressed 

as a distance in nautical miles from the intended centerline 

of a procedure, route, or path. RNP applications also 

account for potential errors at some multiple of RNP level 

(e.g., twice the RNP level). 

Standard RNP Levels 

United States standard values supporting typical RNP 

airspace are shown in Figure 2-56. Other RNP levels as 

identified by ICAO, other states, and the FAA may also be 

used. 

Application of Standard RNP Levels 

United States standard levels of RNP typically used for 

various routes and procedures supporting RNAV operations 

may be based on use of a specific navigational system 

or sensor, such as GPS, or on multi-sensor RNAV systems 

having suitable performance. 

Note: The performance of navigation in RNP refers not only 

to the level of accuracy of a particular sensor or aircraft 

navigation system, but also to the degree of precision 

with which the aircraft is flown. Specific required flight 

procedures may vary for different RNP levels. 

IFR En Route Altitudes 

Minimum En Route Altitudes (MEAs), Minimum Reception 

Altitudes (MRAs), Maximum Authorized Altitudes (MAAs), 

Minimum Obstacle Clearance Altitudes (MOCAs), Minimum 

Turning Altitudes (MTAs) and Minimum Crossing Altitudes 

(MCAs) are established by the FAA for instrument flight 

along Federal airways, as well as some off-airway routes. 

The altitudes are established after it has been determined 

that the NAVAIDs to be used are adequate and so oriented 

on the airways or routes that signal coverage is acceptable, 

and that flight can be maintained within prescribed route 

widths. 

For IFR operations, regulations require that pilots operate 

their aircraft at or above minimum altitudes. Except when 

necessary for takeoff or landing, pilots may not operate an 

aircraft under IFR below applicable minimum altitudes, or 

if no applicable minimum altitude is prescribed, in the case 

of operations over an area designated as mountainous, an 

altitude of 2,000 feet above the highest obstacle within a 

horizontal distance of 4 NM from the course to be flown. In 

any other case, an altitude of 1,000 feet above the highest 

obstacle within a horizontal distance of 4 NM from the 

course to be flown must be maintained as a minimum 

altitude. If both a MEA and a MOCA are prescribed for a 

particular route or route segment, pilots may operate an 

aircraft below the MEA down to, but not below, the MOCA, 

only when within 22 NM of the VOR. When climbing to 

a higher minimum IFR altitude (MIA), pilots must begin 

climbing immediately after passing the point beyond 

which that minimum altitude applies, except when ground 

obstructions intervene, the point beyond which that higher 

minimum altitude applies must be crossed at or above the 

applicable MCA for the VOR. 

If on an IFR flight plan, but cleared by ATC to maintain VFR 

conditions on top, pilots may not fly below minimum en 

route IFR altitudes. Minimum altitude rules are designed to 

ensure safe vertical separation between the aircraft and the 

terrain. These minimum altitude rules apply to all IFR flights, 

whether in IFR or VFR weather conditions, and whether 

assigned a specific altitude or VFR conditions on top. 

Minimum En Route Altitude (MEA) 

The MEA is the lowest published altitude between radio 

fixes that assures acceptable navigational signal coverage 

and meets obstacle clearance requirements between those 

fixes. The MEA prescribed for a Federal airway or segment, 

RNAV low or high route, or other direct route applies to the 

entire width of the airway, segment, or route between the 

radio fixes defining the airway, segment, or route. MEAs 

for routes wholly contained within controlled airspace 

normally provide a buffer above the floor of controlled 

airspace consisting of at least 300 feet within transition 

areas and 500 feet within control areas. MEAs are established 

based upon obstacle clearance over terrain and manmade 

objects, adequacy of navigation facility performance, and 

communications requirements. 

RNAV Minimum En Route Altitude 

RNAV MEAs are depicted on some IFR en route low altitude 

charts, allowing both RNAV and non-RNAV pilots to use the 

same chart for instrument navigation. 

Minimum Reception Altitude (MRA) 

MRAs are determined by FAA flight inspection traversing 

an entire route of flight to establish the minimum altitude 

the navigation signal can be received for the route and for 

off-course NAVAID facilities that determine a fix. When the 

MRA at the fix is higher than the MEA, an MRA is established 

for the fix and is the lowest altitude at which an intersection 

can be determined. 

Maximum Authorized Altitude (MAA) 

An MAA is a published altitude representing the maximum 

usable altitude or flight level for an airspace structure 

2-35 
Figure 2-57. Maximum authorized altitude (MAA). 

Figure 2-58. Minimum obstacle clearance altitude (MOCA). 

Minimum obstacle clearance altitude 

or route segment. [Figure 2-57] It is the highest altitude 

on a Federal airway, jet route, RNAV low or high route, 

or other direct route for which an MEA is designated at 

which adequate reception of navigation signals is assured. 

MAAs represent procedural limits determined by technical 

limitations or other factors, such as limited airspace or 

frequency interference of ground-based facilities. 

Minimum Obstruction Clearance Altitude 

(MOCA) 

The MOCA is the lowest published altitude in effect between 

fixes on VOR airways, off-airway routes, or route segments 

that meets obstacle clearance requirements for the entire 

route segment. [Figure 2-58] This altitude also assures 

acceptable navigational signal coverage only within 22 NM 

of a VOR. The MOCA seen on the en route chart may have 

been computed by adding the required obstacle clearance 

(ROC) to the controlling obstacle in the primary area or 

computed by using a TERPS chart if the controlling obstacle 

is located in the secondary area. This figure is then rounded 

to the nearest 100 foot increment (i.e., 2,049 feet becomes 

2,000, and 2,050 feet becomes 2,100 feet). An extra 1,000 

2-36 
MTA

V330 E to V520 W 16000 V465 NE to 330 W or V520 W 16000 

Figure 2-59. Minimum turning altitude (MTA). 

Centerline 

3.6° 

4.5° 

Fix displacement area 

En route facility

Facility providing intersection radial 

Primary area 

Secondary area 

Figure 2-60. Turning area at the intersection fix with NAVAID distance less than 51 NM. 

2-37 
 

 

feet is added in mountainous areas, in most cases. 

ATC controllers have an important role in helping pilots 

remain clear of obstructions. Controllers are instructed to 

issue a safety alert if the aircraft is in a position that, in their 

judgment, places the pilot in unsafe proximity to terrain, 

obstructions, or other aircraft. Once pilots inform ATC of 

action being taken to resolve the situation, the controller 

may discontinue the issuance of further alerts. A typical 

terrain/obstruction alert may sound like this: “(Aircraft call 

sign ), Low altitude alert. Check your altitude immediately. 

The MOCA in your area is 12,000.” 

Minimum Turning Altitude (MTA) 

Minimum turning altitude (MTA) is a charted altitude 

providing vertical and lateral obstruction clearance based 

on turn criteria over certain fixes, NAVAIDs, waypoints, 

and on charted route segments. [Figure 2-59] When a 

VHF airway or route terminates at a NAVAID or fix, the 

primary area extends beyond that termination point. 

When a change of course on VHF airways and routes is 

necessary, the en route obstacle clearance turning area 

extends the primary and secondary obstacle clearance 

areas to accommodate the turn radius of the aircraft. Since 

turns at or after fix passage may exceed airway and route 

boundaries, pilots are expected to adhere to airway and 

route protected airspace by leading turns early before a 

fix. The turn area provides obstacle clearance for both turn 

anticipation (turning prior to the fix) and flyover protection 

(turning after crossing the fix). This does not violate the 

requirement to fly the centerline of the airway. Many factors 

enter into the construction and application of the turning 

area to provide pilots with adequate obstacle clearance 

protection. These may include aircraft speed, the amount 

of turn versus NAVAID distance, flight track, curve radii, 

MEAs, and MTA. [Figure 2-60] 

Due to increased airspeeds at 10,000 feet MSL or above, an 

expanded area in the vicinity of the turning fix is examined 

to ensure the published MEA is sufficient for obstacle 

clearance. In some locations (normally mountainous), 

terrain/obstacles in the expanded search area may obviate 

the published MEA and necessitate a higher minimum 

altitude while conducting the turning maneuver. Turning 

fixes requiring a higher MTA are charted with a flag along 

with accompanying text describing the MTA restriction. 

[Figure 2-59] 

An MTA restriction normally consists of the ATS route 

leading to the turning fix, the ATS route leading from the 

turning fix, and an altitude (e.g., MTA V330 E TO V520 

W 16000). When an MTA is applicable for the intended 

route of flight, pilots must ensure they are at or above the 

charted MTA prior to beginning the turn and maintain at 

Airway 

number 

or route 

V330 *9500E 

# MTA 

* 13400W JAC 10 

300 MTN ROC RED 

DEL MCA ATIDA 

COME ADD MCA 

AT OSITY DEC MOCA 

INC MCA PRECIP 

TER DEC MOCA 

MEA CARDINAL ALT 

JAC R-251 UNUSABLE 

BYD 10 # CHART: 

MTA V330 E TO 

VS20W 16000 

DEL directional MEA 

MEA CARONIAL ALT 

V330 

Date Office Title Signature 

From 

To 

Idaho Falls, ID VOR/DME 

*Osity, ID 

Osity, ID 

# Jackson, WY VOR/DME 

Routine 

or docket 

number 

GNSS 

MEA 

Change 

over point 

Fix 

MRA/MCA Remarks 

Flight 

inspection 

dates 

Controlling @ 

terrain/Obstruction 

and coordinates 

Tree 6177 @ 

432912.00N/1114118.00W 

Terrain 6077 

432912.00N/1114118.00W 

AAO 12138 (SEC) @ 

434118.30N/1104858.30W 

Terrain 11132 

433900.00N/1105057.00W 

MRA 

MOCA 

MAA 

MEA 

8000 

--7900-­

17500 

8000 

14000 

--13600-­

17500 

14000 

Transmittal of Airways/Route Data 

AJW-3773 Manager Ray Nussear 

Figure 2-61. Minimum turning altitude information located in the remarks section of FAA Form 8260-16 Transmittal of Airways/Route Data. 

2-38 
 

Figure 2-62. Minimum crossing altitude (MCA). 

or above the MTA until joining the centerline of the ATS 

route following the turn. Once established on the centerline 

following the turning fix, the MEA/MOCA determines the 

minimum altitude available for assignment. 

An MTA may also preclude the use of a specific altitude or 

a range of altitudes during a turn. For example, the MTA 

may restrict the use of 10,000 through 11,000 feet MSL. 

In this case, any altitude greater than 11,000 feet MSL is 

unrestricted, as are altitudes less than 10,000 feet MSL 

provided MEA/MOCA requirements are satisfied. 

All MTA information associated with the airway/route 

inbound to the turn fix/facility is put in the remarks section 

of FAA Form 8260-16, Transmittal of Airways/Route Data, 

using the following format [Figure 2-61]: 

#CHART: MTA V330 E TO V520 W 16000


 (Document on V330 FAA Form 8260-16)
 

#CHART: MTA V465 NE TO V330 W OR V520 W 16000

 (Document on V465 FAA Form 8260-16) 

When an MTA is required by FAA Order 8260.3, paragraph 

15-1-5c, enter the MTA information in the REMARKS section 

of FAA Form 8260-2, Radio Fix and Holding Data Record, as 

specified on the appropriate FAA Form 8260-16, Transmittal 

of Airways/Route Data, using the following format: 

MTA: V330 E TO V520 W 16000 

700' 

3200' 

2000' 

6 NM 

4620' MSL 

120' per NM required

Multiply by 6 NM −720 feet 

Maximum Displacement 

MSL 

X

MEA 5200' 

MCA 5900' E 

Obstruction height 4,620' 

Required clearance +2000' 

MOCA at obstruction =6,620' 

Climb value* −720' 

MCA required =5,900' 

* Based upon 6 NM @ 120 feet per NM 

Obstacle Line 

2000' 

Figure 2-63. Minimum crossing altitude (MCA) determination point. 

2-39 
 

MTA: V465 NE TO V330 W OR V520 W 16000 

Minimum Crossing Altitude (MCA) 

An MCA is the lowest altitude at certain fixes at which the 

aircraft must cross when proceeding in the direction of a 

higher minimum en route IFR altitude. [Figure 2-62] When 

applicable, MCAs are depicted on the en route chart. [Figure 

2-59] MCAs are established in all cases where obstacles 

intervene to prevent pilots from maintaining obstacle 

clearance during a normal climb to a higher MEA after 

passing a point beyond which the higher MEA applies. The 

same protected en route area vertical obstacle clearance 

requirements for the primary and secondary areas are 

considered in the determination of the MCA. The standard 

for determining the MCA is based upon the following climb 

gradients and is computed from the flight altitude: 

•	 Sea level through 5,000 feet MSL—150 feet per NM 

•	 5000 feet through 10,000 feet MSL—120 feet per 

NM 

•	 10,000 feet MSL and over—100 feet per NM 

To determine the MCA seen on an en route chart, the 

distance from the obstacle to the fix is computed from 

the point where the centerline of the en route course in 

the direction of flight intersects the farthest displacement 

from the fix. [Figure 2-63] When a change of altitude is 

involved with a course change, course guidance must be 

provided if the change of altitude is more than 1,500 feet 

and/or if the course change is more than 45°, although 

there is an exception to this rule. In some cases, course 

changes of up to 90° may be approved without course 

guidance provided that no obstacles penetrate the 

established MEA requirement of the previous airway or 

route segment. Outside United States airspace, pilots may 

encounter different flight procedures regarding MCA and 

transitioning from one MEA to a higher MEA. In this case, 

pilots are expected to be at the higher MEA crossing the 

fix, similar to an MCA. Pilots must thoroughly review flight 

procedure differences when flying outside United States 

airspace. On IFR en route low altitude charts, routes and 

associated data outside the conterminous United States 

are shown for transitional purposes only and are not part 

of the high altitude jet route and RNAV route systems. 

[Figure 2-64] 

Minimum IFR Altitude (MIA) 

The MIA for operations is prescribed in 14 CFR Part 91. These 

MIAs are published on aeronautical charts and prescribed 

in 14 CFR Part 95 for airways and routes, and in 

14 CFR Part 97 for standard instrument approach 

procedures. If no applicable minimum altitude is prescribed 

NOT FOR NAVIGATION IN CANADA CROSS EACH FIX AT OR 

ABOVE THE HIGHER MINIMUM EN ROUTE

IFR ALTITUDE APPLICABLE TO FLIGHT. 

Figure 2-64. En route chart minimum crossing altitude data (outside of the U.S.). 

2-40 
SAMPLE NOT 

FOR ACTUAL USE

 

 

 

Figure 2-65. MVA chart. 

in 14 CFR Parts 95 or 97, the following MIA applies: In 

designated mountainous areas, 2,000 feet above the 

highest obstacle within a horizontal distance of 4 NM 

from the course to be flown; or other than mountainous 

areas, 1,000 feet above the highest obstacle within a 

horizontal distance of 4 NM from the course to be flown; or 

as otherwise authorized by the Administrator or assigned 

by ATC. MIAs are not flight checked for communication. 

Minimum Vectoring Altitudes (MVA) 

MVAs are established for use by ATC when radar ATC is 

exercised. The MVA provides 1,000 feet of clearance above 

the highest obstacle in non-mountainous areas and 2,000 

20 

40 

60 

80 

100 

120 

RKS 160 

RKS 080

RKS 003

RKS 269 

RKS 325 

211 

001 

065 

110 

180 

270 

10,000 

RIW 

15,800 

14,500 

12,000 

13,700 

10,700 

11,000 

12,000 12,400

15,500 

14,200 

11,000 13,800 

13,300 

12,300 

14,500 

243 

065 

142 

CKW 

VEL 

FBR 

RKS 

070 

feet above the highest obstacle in designated mountainous 

areas. Because of the ability to isolate specific obstacles, 

some MVAs may be lower than MEAs, MOCAs, or other 

minimum altitudes depicted on charts for a given location. 

While being radar vectored, IFR altitude assignments by 

ATC are normally at or above the MVA. 

Air traffic controllers use MVAs only when they are assured 

an adequate radar return is being received from the aircraft. 

Charts depicting MVAs are available to controllers and have 

recently become available to pilots. They can be found 

at http://www.faa.gov/air_traffic/flight_info/aeronav/ 

digital_products/mva_mia/ Situational Awareness is 

2-41 
 

 

 

IFR 

EVEN 

2,000' 

Intervals 

begin at 

18,000' MSL 

VFR or 

VFR-ON-TOP 

EVEN 

2,000' 

Intervals 

begin at 

FL 185 

IFR 

ODD 

2,000' 

Intervals 

begin at 

FL 190 

VFR or 

VFR-ON-TOP 

ODD 

2,000' 

Intervals 

begin at 

FL 195 

359

M 

180° 

0° 

179

M 

18,000' MSL to flight level 290 

IFR 

EVEN 

4,000' 

Intervals 

begin at 

FL 310 

VFR or 

VFR-ON-TOP 

4,000' 

Intervals 

begin at 

FL 320 

IFR 

4,000' 

Intervals 

begin at 

FL 290 

VFR or 

VFR-ON-TOP 

4,000' 

Intervals 

begin at 

FL 300 

359

M 

180° 

0° 

179

M 

Flight level 290 and above 

IFR 

EVEN 

thousands 

VFR or 

ON-TOP 

EVEN 

thousands 

plus 

500' 

IFR 

ODD 

thousands 

VFR or 

ON-TOP 

ODD 

thousands 

plus 

500' 

359

M 

180° 

0° 

179

M 

Cruising altitudes - U.S. 

IFR within controlled airspace as assigned by ATC 

For additional symbol information 

refer to the chart user’s guide. 

VFR above 3000' AGL unless otherwise 

authorized by ATC IFR outside controlled 

airspace all courses are magnetic 

NO VFR FLIGHTS WITHIN 

CLASS A AIRSPACE 

CRUISING ALTITUDES 

IFR within controlled airspace as assigned by ATC 

VFR above 3,000' AGL unless otherwise 

authorized by ATC IFR outside controlled 

airspace all courses are magnetic 

Figure 2-66. Cruising altitude or flight level. 

always important, especially when being radar vectored 

during a climb into an area with progressively higher MVA 

sectors, similar to the concept of MCA. Except where diverse 

vector areas have been established, when climbing, pilots 

should not be vectored into a sector with a higher MVA 

unless at or above the next sector’s MVA. Where lower 

MVAs are required in designated mountainous areas to 

achieve compatibility with terminal routes or to permit 

vectoring to an instrument approach procedure, 1,000 feet 

of obstacle clearance may be authorized with the use of 

Airport Surveillance Radar (ASR). The MVA provides at least 

300 feet above the floor of controlled airspace. The MVA 

charts are developed to the maximum radar range. Sectors 

provide separation from terrain and obstructions. Each MVA 

chart has sectors large enough to accommodate vectoring 

of aircraft within the sector at the MVA. [Figure 2-65] 

IFR Cruising Altitude or Flight Level 

In controlled airspace, pilots must maintain the altitude or 

flight level assigned by ATC, although if the ATC clearance 

assigns “VFR conditions on-top,” an altitude or flight level as 

prescribed by 14 CFR Part 91, § 91.159 must be maintained. 

In uncontrolled airspace (except while in a holding pattern 

of two minutes or less or while turning) if operating an 

aircraft under IFR in level cruising flight, an appropriate 

altitude as depicted in the legend of IFR en route high 

and low altitude charts must be maintained. [Figure 2-66] 

When operating on an IFR flight plan below 18,000 feet 

MSL in accordance with a VFR-on-top clearance, any VFR 

cruising altitude appropriate to the direction of flight 

between the MEA and 18,000 feet MSL may be selected that 

allows the flight to remain in VFR conditions. Any change in 

altitude must be reported to ATC, and pilots must comply 

with all other IFR reporting procedures. VFR-on-top is not 

authorized in Class A airspace. When cruising below 18,000 

feet MSL, the altimeter must be adjusted to the current 

setting, as reported by a station within 100 NM of your 

position. In areas where weather-reporting stations are 

more than 100 NM from the route, the altimeter setting of 

a station that is closest may be used. 

During IFR flight, ATC advises flights periodically of the 

current altimeter setting, but it remains the responsibility 

of the pilot or flight crew to update altimeter settings in a 

timely manner. Altimeter settings and weather information 

2-42 
 

 

are available from weather reporting facilities operated or 

approved by the U.S. National Weather Service, or a source 

approved by the FAA. Some commercial operators have 

the authority to act as a government-approved source of 

weather information, including altimeter settings, through 

certification under the FAA’s Enhanced Weather Information 

System. 

Flight level operations at or above 18,000 feet MSL require 

the altimeter to be set to 29.92 inches of mercury (" Hg). A 

flight level (FL) is defined as a level of constant atmospheric 

pressure related to a reference datum of 29.92 " Hg. Each 

flight level is stated in three digits that represent hundreds of 

feet. For example, FL 250 represents an altimeter indication 

of 25,000 feet. Conflicts with traffic operating below 18,000 

feet MSL may arise when actual altimeter settings along the 

route of flight are lower than 29.92 " Hg. Therefore, 14 CFR 

Part 91, § 91.121 specifies the lowest usable flight levels for 

a given altimeter setting range. 

Reduced Vertical Separation Minimums (RSVM) 

Reduced vertical separation minimums (RVSM) is a term 

used to describe the reduction of the standard vertical 

separation required between aircraft flying at levels 

between FL 290 (29,000 feet) and FL 410 (41,000 feet) 

from 2,000 feet to 1,000 feet. The purpose; therefore, 

increases the number of aircraft that can safely fly in a 

particular volume of airspace. Historically, standard vertical 

separation was 1,000 feet from the surface to FL 290, 2,000 

feet from FL 290 to FL 410 and 4,000 feet above this. This 

was because the accuracy of the pressure altimeter (used 

to determine altitude) decreases with height. Over time, 

air data computers (ADCs) combined with altimeters have 

become more accurate and autopilots more adept at 

maintaining a set level; therefore, it became apparent that 

for many modern aircraft, the 2,000-foot separation was not 

required . It was, therefore, proposed by ICAO that this be 

reduced to 1,000 feet. 

Between 1997 and 2005, RVSM was implemented in all of 

Europe, North Africa, Southeast Asia, North America, South 

America, and over the North Atlantic, South Atlantic, and 

Pacific Oceans. The North Atlantic implemented initially in 

March 1997, at FL 330 through FL 370. The entire western 

hemisphere implemented RVSM FL 290–FL 410 on January 

20, 2005. 

Only aircraft with specially certified altimeters and 

autopilots may fly in RVSM airspace, otherwise the aircraft 

must fly lower or higher than the airspace, or seek special 

exemption from the requirements. Additionally, aircraft 

operators (airlines or corporate operators) must receive 

specific approval from the aircraft’s state of registry in 

order to conduct operations in RVSM airspace. Non-RVSM 

approved aircraft may transit through RVSM airspace 

provided they are given continuous climb throughout the 

designated airspace, and 2,000 feet vertical separation is 

provided at all times between the non-RVSM flight and all 

others for the duration of the climb/descent. 

Critics of the change were concerned that by reducing 

the space between aircraft, RVSM may increase the 

number of mid-air collisions and conflicts. In the ten 

years since RVSM was first implemented, not one 

collision has been attributed to RVSM. In the United 

States, this program was known as the Domestic 

Reduced Vertical Separation Minimum (DRVSM). 

Cruise Clearance 

The term “cruise” may be used instead of “maintain” to 

assign a block of airspace to an aircraft. The block extends 

from the minimum IFR altitude up to and including the 

altitude that is specified in the cruise clearance. On a cruise 

clearance, you may level off at any intermediate altitude 

within this block of airspace. You are allowed to climb or 

descend within the block at your own discretion. However, 

once you start descent and verbally report leaving an 

altitude in the block to ATC, you may not return to that 

altitude without an additional ATC clearance. A cruise 

clearance also authorizes you to execute an approach at 

the destination airport. 

Lowest Usable Flight Level 

When the barometric pressure is 31.00 " Hg or less and 

pilots are flying below 18,000 feet MSL, use the current 

reported altimeter setting. When an aircraft is en route 

on an instrument flight plan, air traffic controllers furnish 

this information at least once while the aircraft is in the 

controller’s area of jurisdiction. When the barometric 

pressure exceeds 31.00 " Hg, the following procedures are 

placed in effect by NOTAM defining the geographic area 

affected: Set 31.00 " Hg for en route operations below 

18,000 feet MSL and maintain this setting until beyond 

the affected area. ATC issues actual altimeter settings and 

advises pilots to set 31.00 " Hg in their altimeter, for en route 

operations below 18,000 feet MSL in affected areas. If an 

aircraft has the capability of setting the current altimeter 

setting and operating into airports with the capability of 

measuring the current altimeter setting, no additional 

restrictions apply. At or above 18,000 feet MSL, altimeters 

should be set to 29.92 " Hg (standard setting). Additional 

procedures exist beyond the en route phase of flight. 

The lowest usable flight level is determined by the 

atmospheric pressure in the area of operation. As local 

altimeter settings fall below 29.92 " Hg, pilots operating 

in Class A airspace must cruise at progressively higher 

indicated altitudes to ensure separation from aircraft 

2-43 
 

FAA AIR SERVICE OUTSIDE U.S. AIRSPACE

IS PROVIDED IN ACCORDANCE WITH

ARTICLE 12 AND ANNEX 11 OF ICAO

CONVENTION. ICAO CONVENTION NOT

APPLICABLE TO STATE AIRCRAFT BUT

COMPLIANCE WITH ICAO STANDARDS

NOT FOR NAVIGATION

AND PRACTICES IS ENCOURAGED. 

MONCTON FIR

CZQM 

ALTIMETER

QNH 

QNE 

CRABB

N42°13.00 ́

W65°44.00 ́ 

Figure 2-67. Altimeter setting changes. 

operating in the low altitude structure as follows: 

Current Altimeter Setting Lowest Usable Flight Level 

29.92 or higher 180 

29.91 to 29.42 185 

29.41 to 28.92 190 

28.91 to 28.42 195 

28.41 to 27.91 200 

When the minimum altitude, as prescribed in 14 CFR Part 

91, § 91.159 and 91.177, is above 18,000 feet MSL, the 

lowest usable flight level is the flight level equivalent of 

the minimum altitude plus the number of feet specified 

according to the lowest flight level correction factor as 

follows: 

Altimeter Setting Correction Factor 

29.92 or higher — 

29.91 to 29.42 500 feet 

Altimeter Setting Correction Factor 

29.41 to 28.92 1,000 feet 

28.91 to 28.42 1,500 feet 

28.41 to 27.91 2,000 feet 

27.91 to 27.42 2,500 feet 

Operations in Other Countries 

When flight crews transition from the U.S. NAS to another 

country’s airspace, they should be aware of differences not 

only in procedures but also airspace. For example, when 

flying into Canada as depicted in Figure 2-67, notice the 

change from transition level (QNE) to transition altitude 

(QNH) when flying north-bound into the Moncton flight 

information region (FIR). 

Operations in international airspace demand that pilots 

are aware of, and understand the use of, the three types 

of altimeter settings. Most overseas airports give altimeter 

2-44 
 

 

RADAR/NON-RADAR REPORTS 

These reports should be made at all times without a specific ATC request. 

Leaving one assigned flight altitude or flight level for another 

VFR-on-top change in altitude 

Leaving any assigned holding fix or point 

Missed approach 

Unable to climb or descend at least 500 fpm 

TAS variation from filed speed of 5% or 10 knots, whichever 

is greater 

Time and altitude or flight level upon reaching a holding fix 

or clearance limit 

Loss of Nav/Comm capability (required by Part 91.187) 

Unforecast weather conditions or other information relating 

to the safety of flight (required by Part 91.183) 

"Marathon 564, leaving 8,000, climb to 10,000." 

"Marathon 564, VFR-on-top, climbing to 10,500." 

"Marathon 564, leaving FARGO Intersection." 

"Marathon 564, missed approach, request clearance to Chicago." 

"Marathon 564, maximum climb rate 400 feet per minute." 

"Marathon 564, advises TAS decrease to140 knots." 

"Marathon 564, FARGO Intersection at 05, 10,000, holding east." 

"Marathon 564, ILS receiver inoperative." 

"Marathon 564, experiencing moderate turbulence at 10,000." 

NON-RADAR REPORTS 

When you are not in radar contact, these reports should be made without a specific request from ATC. 

Leaving FAF or OM inbound on final approach 

Revised ETA of more than three minutes 

"Marathon 564, outer marker inbound, leaving 2,000." 

"Marathon 564, revising SCURRY estimate to 55." 

REPORTS EXAMPLE 

REPORTS EXAMPLE 

Figure 2-68. ATC reporting procedures. 

settings in hectopascals (hPa) (millibars). Therefore, it is 

imperative that pilots or on-board equipment are able 

to accurately convert inches of mercury to hPa, or hPa to 

inches of mercury. 

Altitude Above Ground (QFE) 

A local altimeter setting equivalent to the barometric 

pressure measured at an airport altimeter datum, usually 

signifying the approach end of the runway is in use. At the 

airport altimeter datum, an altimeter set to QFE indicates 

zero altitude. If required to use QFE altimetry, altimeters 

are set to QFE while operating at or below the transition 

altitude and below the transition level. On the airport, the 

altimeter will read “0” feet. 

Barometric Pressure for Standard Altimeter 

Setting (QNE) 

Use the altimeter setting (en route) at or above the 

transition altitude (FL 180 in the United States). The 

altimeter setting is always 29.92 inches of mercury/1013.2 

hPa for a QNE altitude. Transition levels differ from country 

to country and pilots should be particularly alert when 

making a climb or descent in a foreign area. 

Barometric Pressure for Local Altimeter Setting 

(QNH) 

A local altimeter setting equivalent to the barometric 

pressure measured at an airport altimeter datum and 

corrected to sea level pressure. At the airport altimeter 

datum, an altimeter set to QNH indicates airport elevation 

above mean sea level (MSL). Altimeters are set to QNH 

while operating at and below the transition altitude and 

below the transition level. 

For flights in the vicinity of airports, express the vertical 

position of aircraft in terms of QNH or QFE at or below the 

transition altitude and in terms of QNE at or above the 

transition level. While passing through the transition layer, 

express vertical position in terms of FLs when ascending 

and in terms of altitudes when descending. 

When an aircraft that receives a clearance as number one 

to land completes its approach using QFE, express the 

vertical position of the aircraft in terms of height above 

the airport elevation during that portion of its flight for 

which you may use QFE. 

It is important to remember that most pressure altimeters 

are subject to mechanical, elastic, temperature, and 

installation errors. In addition, extremely cold temperature 

differences may also require altimeter correction factors 

as appropriate. 

2-45 
 

 

En Route Reporting Procedures 

In addition to acknowledging a handoff to another Center 

en route controller, there are reports that should be made 

without a specific request from ATC. Certain reports should 

be made at all times regardless of whether a flight is in radar 

contact with ATC, while others are necessary only if radar 

contact has been lost or terminated. [Figure 2-68] 

Non-Radar Position Reports 

If radar contact has been lost or radar service terminated, 

the CFRs require pilots to provide ATC with position reports 

over designated VORs and intersections along their route 

of flight. These compulsory reporting points are depicted 

on IFR en route charts by solid triangles. Position reports 

over fixes indicated by open triangles are noncompulsory 

reporting points and are only necessary when requested by 

ATC. If on a direct course that is not on an established airway, 

report over the fixes used in the flight plan that define 

the route, since they automatically become compulsory 

reporting points. Compulsory reporting points also apply 

when conducting an IFR flight in accordance with a VFRon-top clearance. 

Whether a route is on an airway or direct, position reports 

are mandatory in a non-radar environment, and they 

must include specific information. A typical position 

report includes information pertaining to aircraft position, 

expected route, and ETA. When a position report is to be 

made passing a VOR radio facility, the time reported should 

be the time at which the first complete reversal of the TO/ 

FROM indicator is accomplished. When a position report is 

made passing a facility by means of an airborne ADF, the 

time reported should be the time at which the indicator 

makes a complete reversal. When an aural or a light panel 

indication is used to determine the time passing a reporting 

point, such as a fan marker, Z marker, cone of silence or 

intersection of range courses, the time should be noted 

when the signal is first received and again when it ceases. 

The mean of these two times should then be taken as the 

actual time over the fix. If a position is given with respect to 

distance and direction from a reporting point, the distance 

and direction should be computed as accurately as possible. 

Except for terminal area transition purposes, position 

reports or navigation with reference to aids not established 

for use in the structure in which flight is being conducted 

are not normally required by ATC. 

Flights in a Radar Environment 

When informed by ATC that their aircraft are in “Radar 

Contact,” pilots should discontinue position reports over 

designated reporting points. They should resume normal 

position reporting when ATC advises “radar contact lost” 

or “radar service terminated.” ATC informs pilots that they 

are in radar contact: 

1.	 When their aircraft is initially identified in the 

ATC system; and 

2.	 When radar identification is reestablished after 

radar service has been terminated or radar 

contact lost. 

Subsequent to being advised that the controller has 

established radar contact, this fact is not repeated to 

the pilot when handed off to another controller. At 

times, the aircraft identity is confirmed by the receiving 

controller; however, this should not be construed to 

mean that radar contact has been lost. The identity of 

transponder equipped aircraft is confirmed by asking 

the pilot to “ident,” “squawk standby,” or to change 

codes. Aircraft without transponders are advised of 

their position to confirm identity. In this case, the pilot 

is expected to advise the controller if in disagreement 

with the position given. Any pilot who cannot confirm 

the accuracy of the position given because of not being 

tuned to the NAVAID referenced by the controller 

should ask for another radar position relative to the 

tuned in NAVAID. 

Position Report Items
 

Position reports should include the following items: 


1.	 Aircraft identification 

2.	 Position 

3.	 Time 

4.	 Altitude or flight level (include actual altitude 

or flight level when operating on a clearance 

specifying VFR-on-top) 

5.	 Type of flight plan (not required in IFR position 

reports made directly to ARTCCs or approach 

control) 

6.	 ETA and name of next reporting point 

7.	 The name only of the next succeeding reporting 

point along the route of flight 

8.	 Pertinent remarks 

Additional Reports 

The following reports should be made at all times to 

ATC or Flight Service facilities without a specific ATC 

request: 

1.	 When vacating any previously assigned altitude 

or flight level for a newly assigned altitude or 

flight level. 

2.	 When an altitude change is made if operating 

on a clearance specifying VFR-on-top. 

2-46 
 

3.	 When unable to climb/descend at a rate of a least 

500 feet per minute (fpm). 

4.	 When approach has been missed. (Request clearance 

for specific action (i.e., to alternative airport, another 

approach). 

5.	 Change in the average true airspeed (at cruising 

altitude) when it varies by 5 percent or 10 knots 

(whichever is greater) from that filed in the flight 

plan. 

6.	 The time and altitude or flight level upon reaching 

a holding fix or point to which cleared. 

7.	 When leaving any assigned holding fix or point. 

Note: The reports stated in subparagraphs 6 and 

7 may be omitted by pilots of aircraft involved in 

instrument training at military terminal area facilities 

when radar service is being provided. 

8.	 Any loss, in controlled airspace, of VOR, TACAN, 

ADF, low frequency navigation receiver capability, 

GPS anomalies while using installed IFR-certified 

GPS/GNSS receivers, complete or partial loss of ILS 

receiver capability or impairment of air/ground 

communications capability. Reports should include 

aircraft identification, equipment affected, degree 

to which the capability to operate under IFR in the 

ATC system is impaired, and the nature and extent 

of assistance desired from ATC. 

9.	 Any information relating to the safety of flight. 

Other equipment installed in an aircraft may impair your 

ability to safely operate under IFR. If a malfunction of 

such equipment (e.g., weather radar) affects any safety or 

IFR capability, reports should be made as stated above. 

When reporting GPS anomalies, be very specific and 

include the location, altitude, and duration of the anomaly. 

Deliberate GPS interference or outage areas resulting from 

pre-approved government tests will be disseminated in 

NOTAMs. These outages should not be reported to ATC, 

as this condition is known and not an anomaly. See also 

AIM 1-1-13. 

Communication Failure 

Two-way radio communication failure procedures for IFR 

operations are outlined in 14 CFR Part 91, § 91.185. Unless 

otherwise authorized by ATC, pilots operating under IFR 

are expected to comply with this regulation. Expanded 

procedures for communication failures are found in the 

Aeronautical Information Manual (AIM). Pilots can use the 

transponder to alert ATC to a radio communication failure by 

squawking code 7600. [Figure 2-69] If only the transmitter 

is inoperative, listen for ATC instructions on any operational 

receiver, including the navigation receivers. It is possible ATC 

may try to make contact with pilots over a VOR, VORTAC, 

NDB, or localizer frequency. In addition to monitoring 

NAVAID receivers, attempt to reestablish communications 

by contacting ATC on a previously assigned frequency or 

calling an FSS. 

The primary objective of the regulations governing 

communication failures is to preclude extended IFR 

no-radio operations within the ATC system since these 

operations may adversely affect other users of the airspace. 

If the radio fails while operating on an IFR clearance, but 

in VFR conditions, or if encountering VFR conditions at 

any time after the failure, continue the flight under VFR 

conditions, if possible, and land as soon as practicable. The 

requirement to land as soon as practicable should not be 

construed to mean as soon as possible. Pilots retain the 

prerogative of exercising their best judgment and are not 

required to land at an unauthorized airport, at an airport 

unsuitable for the type of aircraft flown, or to land only 

When an aircraft squawks code 7600 during a two-way radio 

communication failure, the information block on the radar 

screen flashes RDOF (radio failure) to alert the controller. 

Figure 2-69. Two-way radio communications failure transponder code. 

minutes short of their intended destination. However, if 

IFR conditions prevail, pilots must comply with procedures 

designated in the CFRs to ensure aircraft separation. 

If pilots must continue their flight under IFR after 

experiencing two-way radio communication failure, they 

should fly one of the following routes: 

•	 The route assigned by ATC in the last clearance 

received. 

•	 If being radar vectored, the direct route from the 

point of radio failure to the fix, route, or airway 

specified in the radar vector clearance. 

•	 In the absence of an assigned route, the route ATC 

has advised to expect in a further clearance. 

•	 In the absence of an assigned or expected route, the 

route filed in the flight plan. 

2-47 
 

 

 

 

 

It is also important to fly a specific altitude should two-way 

radio communications be lost. The altitude to fly after a 

communication failure can be found in 14 CFR Part 91, § 

91.185 and must be the highest of the following altitudes 

for each route segment flown. 

•	 The altitude or flight level assigned in the last ATC 

clearance. 

•	 The minimum altitude or flight level for IFR 

operations. 

•	 The altitude or flight level ATC has advised to expect 

in a further clearance. 

In some cases, the assigned or expected altitude may not be as 

high as the MEA on the next route segment. In this situation, 

pilots normally begin a climb to the higher MEA when they 

reach the fix where the MEA rises. If the fix also has a published 

MCA, they start the climb so they are at or above the MCA 

when reaching the fix. If the next succeeding route segment 

has a lower MEA, descend to the applicable altitude either 

the last assigned altitude or the altitude expected in a further 

clearance—when reaching the fix where the MEA decreases. 

ARTCC Radio Frequency Outage 

ARTCCs normally have at least one back-up radio receiver 

and transmitter system for each frequency that can usually 

be placed into service quickly with little or no disruption of 

ATC service. Occasionally, technical problems may cause a 

delay but switchover seldom takes more than 60 seconds. 

When it appears that the outage is not quickly remedied, 

the ARTCC usually requests a nearby aircraft, if there is 

one, to switch to the affected frequency to broadcast 

communications instructions. It is important that the pilot 

wait at least one minute before deciding that the ARTCC has 

actually experienced a radio frequency failure. When such 

an outage does occur, the pilot should, if workload and 

equipment capability permit, maintain a listening watch 

on the affected frequency while attempting to comply with 

the following recommended communications procedures: 

1.	 If two-way communications cannot be established 

with the ARTCC after changing frequencies, a pilot 

should attempt to re-contact the transferring 

controller for the assignment of an alternative 

frequency or other instructions. 

2.	 When an ARTCC radio frequency failure occurs after 

two-way communications have been established, 

the pilot should attempt to reestablish contact with 

the center on any other known ARTCC frequency, 

preferably that of the next responsible sector when 

practicable, and ask for instructions. However, 

when the next normal frequency change along 

the route is known to involve another ATC facility, 

the pilot should contact that facility, if feasible, 

for instructions. If communications cannot be 

reestablished by either method, the pilot is expected 

to request communication instructions from the FSS 

appropriate to the route of flight. 

Note: The exchange of information between an aircraft 

and an ARTCC through an FSS is quicker than relay via 

company radio because the FSS has direct interphone 

lines to the responsible ARTCC sector. Accordingly, 

when circumstances dictate a choice between the two 

during an ARTCC frequency outage relay via FSS radio is 

recommended. 

Climbing and Descending En Route 

When ATC issues a clearance or instruction, pilots are 

expected to execute its provisions upon receipt. In some 

cases, ATC includes words that modify their expectation. 

For example, the word “immediately” in a clearance or 

instruction is used to impress urgency to avoid an imminent 

situation, and expeditious compliance is expected and 

necessary for safety. The addition of a climb point or time 

restriction, for example, does not authorize pilots to deviate 

from the route of flight or any other provision of the ATC 

clearance. If the pilot receives the term “climb at pilot’s 

discretion” in the altitude information of an ATC clearance, 

it means that the pilot has the option to start a climb when 

they desire and are authorized to climb at any rate, and to 

temporarily level off at any intermediate altitude as desired, 

although once you vacate an altitude, you may not return to 

that altitude. When ATC has not used the term nor imposed 

any climb restrictions, pilots should climb promptly on 

acknowledgment of the clearance. Climb at an optimum 

rate consistent with the operating characteristics of the 

aircraft to 1,000 feet below the assigned altitude, and then 

attempt to climb at a rate of between 500 and 1,500 fpm 

until the assigned altitude is reached. If at any time the 

pilot is unable to climb at a rate of at least 500 fpm, advise 

ATC. If it is necessary to level off at an intermediate altitude 

during climb, advise ATC. 

When ATC issues the instruction, “Expedite climb,” this 

normally indicates that the pilot should use the approximate 

best rate of climb without an exceptional change in aircraft 

handling characteristics. Normally controllers inform pilots 

of the reason for an instruction to expedite. If flying a 

turbojet aircraft equipped with afterburner engines, such as 

a military aircraft, pilots should advise ATC prior to takeoff 

if intending to use afterburning during the climb to the en 

route altitude. Often, the controller may be able to plan 

traffic to accommodate a high performance climb and allow 

the pilot to climb to the planned altitude without “expedite” 

clearance from restriction. If you receive an ATC instruction, 

and your altitude to maintain is subsequently changed 

or restated without an expedite instruction, the expedite 

2-48 
 

 

 

instruction is canceled. 

During en route climb, as in any other phase of flight, 

it is essential that you clearly communicate with ATC 

regarding clearances. In the following example, a flight crew 

experienced an apparent clearance readback/hearback 

error, that resulted in confusion about the clearance and, 

ultimately, to inadequate separation from another aircraft. 

“Departing IFR, clearance was to maintain 5,000 feet, 

expect 12,000 in 10 minutes.” After handoff to Center, the 

pilot understood and read back, “Leaving 5,000 turn left 

heading 240° for vector on course.” The pilot turned to the 

assigned heading climbing through 5,000 feet. At 5,300 feet, 

Center advised assigned altitude was 5,000 feet. The pilot 

immediately descended to 5,000. Center then informed 

the pilot that there was traffic at 12 o’clock and a mile at 

6,000. After passing traffic, a higher altitude was assigned 

and climb resumed. The pilot then believed the clearance 

was probably "reaching" 5,000, etc. Even the readback to the 

controller with "leaving" did not catch the different wording. 

“Reaching” and “leaving” are commonly used ATC terms 

having different usages. They may be used in clearances 

involving climbs, descents, turns, or speed changes. In the 

flight deck, the words “reaching” and “leaving” sound much 

alike. 

For altitude awareness during climb, pilots often call out 

altitudes on the flight deck. The pilot monitoring may call 

2,000 and 1,000 feet prior to reaching an assigned altitude. 

The callout may be, “two” climbing through the transit 

to go altitude (QNH), both pilots set their altimeters to 

29.92 inches of mercury and announce “2992 inches” (or 

‘standard,’ on some aircraft) and the flight level passing. 

For example, “2992 inches” (standard), flight level one 

eight zero. The second officer on three pilot crews may 

ensure that both pilots have inserted the proper altimeter 

setting. On international flights, pilots must be prepared 

to differentiate, if necessary, between barometric pressure 

equivalents with inches of mercury, and millibars or 

hectopascals, to eliminate any potential for error. For 

example, 996 millibars erroneously being set as 2996. 

For a typical IFR flight, the majority of in-flight time often 

is flown in level flight at cruising altitude from top of climb 

(TOC) to top of descent (TOD). Generally, TOD is used in 

airplanes with a FMS and represents the point at which 

descent is first initiated from cruise altitude. FMS also 

assist in level flight by cruising at the most fuel saving 

speed, providing continuing guidance along the flight plan 

route including great circle direct routes, and continuous 

evaluation and prediction of fuel consumption along with 

changing clearance data. 

Secondary area 

Primary area holding pattern airspace area Fix displacement area 

Facility 

Facility 

Figure 2-70. Holding pattern design criteria template. 

2-49 
 

 

NOT FOR NAVIGATION

"...Hold southeast 

of PINNE Intersection as published. 

Expect further clearance at 1645." 

There are at least three items in a clearance for a charted holding pattern: 

• Direction to hold from the holding fix 

• Holding fix 

• Expect further clearance time 

A clearance for an uncharted holding pattern contains additional information: 

• Direction to hold from holding fix 

• Holding fix 

• The holding course (a specified radial, 

magnetic bearing, airway or route number) 

• The outbound leg length in minutes or 

nautical miles when DME is used 

• Nonstandard pattern, if used 

• Expect further clearance time 

"...Hold west 

of Horst Intersection 

on Victor 8 

5 mile legs 

left turns 

expect further clearance at 1430." 

Figure 2-71. ATC holding instructions. 

Aircraft Speed and Altitude 

During the en route descent phase of flight, an additional 

benefit a FMS is that it provides fuel saving idle thrust 

descent to your destination airport. This allows an 

uninterrupted profile descent from level cruising altitude 

to an appropriate MIA, except where level flight is required 

for speed adjustment. Controllers anticipate and plan that 

Figure 2-72. Clearance limit holding. 

CHERRELYN 

D 

( H )117.2 CHL 

331° 

269° 

221°

126°

V214 

the pilot may level off at 10,000 feet MSL on descent to 

comply with the 14 CFR Part 91 indicated airspeed limit of 

250 knots. Leveling off at any other time on descent may 

seriously affect air traffic handling by ATC. It is imperative 

that pilots make every effort to fulfill ATC expected actions 

on descent to aid in safely handling and expediting air 

traffic. 

ATC issues speed adjustments if the flight is being radar 

controlled to achieve or maintain required or desired 

spacing. They express speed adjustments in terms of knots 

based on indicated airspeed in 10 knot increments except 

that at or above FL 240 speeds may be expressed in terms 

of Mach numbers in 0.01 increments. The use of Mach 

numbers by ATC is restricted to turbojets. If complying 

with speed adjustments, pilots are expected to maintain 

that speed within plus or minus 10 knots or 0.02 Mach. 

Speed and altitude restrictions in clearances are subject 

to misinterpretation, as evidenced in this case where a 

corporate flight crew treated instructions in a published 

procedure as a clearance. The aircraft was at FL 310 and 

had already programmed the ‘expect-crossing altitude’ of 

2-50 
 

 

 

Maximum Holding Airspeed: KIAS 2 6 5

Maximum Holding Airspeed: KIAS 2 3 0

Maximum Holding Airspeed: KIAS 2 0 0

14,001' 

MSL 

14,000' 

MSL 

6,000' 

MSL 

Minimum 

Holding 

Altitude 

(MHA) 

6,001' 

MSL 

Figure 2-73. Maximum holding speeds for different altitudes. 

17,000 feet at the VOR. When the altitude alerter sounded, 

the pilot advised Center that we were leaving FL 310. ATC 

acknowledged with a “Roger.” At FL 270, Center questioned 

the pilot about the aircrafts descent. The pilot told the 

controller that the reason for the descent was to cross the 

VOR at 17,000 feet. ATC advised the pilot that he did not 

have clearance to descend. What the pilot thought was a 

clearance was in fact an “expect”clearance. Whenever pilots 

are in doubt about a clearance it is imperative they request 

clarity from ATC. Also, the term “Roger” only means that ATC 

received the transmission, not that they understood the 

transmission. “Expect” altitudes are published for planning 

purposes and are not considered crossing restrictions until 

verbally issued by ATC. 

En Route Holding Procedures 

The criteria for holding pattern airspace is developed 

both to provide separation of aircraft, as well as obstacle 

clearance. The alignment of holding patterns typically 

coincides with the flight course you fly after leaving the 

holding fix. For level holding, a minimum of 1,000 feet 

obstacle clearance is provided throughout the primary 

area. In the secondary area, 500 feet of obstacle clearance 

is provided at the inner edge, tapering to zero feet at the 

outer edge. Allowance for precipitous terrain is considered, 

and the altitudes selected for obstacle clearance may be 

rounded to the nearest 100 feet. When criteria for a climb 

in hold are applied, no obstacle penetrates the holding 

surface. [Figure 2-70] 

There are many factors that affect aircraft during holding 

maneuvers, including navigational aid ground and airborne 

tolerance, effect of wind, flight procedures, application of 

ATC, outbound leg length, maximum holding airspeeds, 

fix to NAVAID distance, DME slant range effect, holding 

airspace size, and altitude holding levels. 

ATC Holding Instructions 

When controllers anticipate a delay at a clearance limit or 

fix, pilots are usually issued a holding clearance at least 

five minutes before the ETA at the clearance limit or fix. If 

the holding pattern assigned by ATC is depicted on the 

appropriate aeronautical chart, pilots are expected to 

hold as charted. In the following example, the controller 

issues a holding clearance that includes the name of the 

fix, directs the pilot to hold as charted, and includes an 

expect further clearance (EFC) time. “Marathon five sixty 

four, hold east of MIKEY Intersection as published, expect 

further clearance at 1521.” 

When ATC issues a clearance requiring you to hold at a fix 

where a holding pattern is not charted, pilots are issued 

complete holding instructions. The holding instructions 

include the direction from the fix, name of the fix, course, 

leg length, if appropriate, direction of turns (if left turns 

are required), and the EFC time. Pilots are required to 

maintain the last assigned altitude unless a new altitude is 

specifically included in the holding clearance and should 

fly right turns unless left turns are assigned. Note that all 

holding instructions should include an EFC time. In the 

event that two-way radio communication is lost, the EFC 

allows the pilot to depart the holding fix at a definite time. 

Pilots should plan the last lap of the holding pattern to 

leave the fix as close as possible to the exact time. [Figure 

2-71] 

When approaching the clearance limit and you have 

not received holding instructions from ATC, pilots are 

expected to follow certain procedures. First, call ATC 

and request further clearance before reaching the fix. If 

further clearance cannot be obtained, pilots are expected 

to hold at the fix in compliance with the charted holding 

pattern. If a holding pattern is not charted at the fix, pilots 

are expected to hold on the inbound course using right 

turns. This procedure ensures that ATC provides adequate 

separation. [Figure 2-72] For example, the aircraft is heading 

eastbound on V214 and the Cherrelyn VORTAC is the 

clearance limit and the pilot has not been able to obtain 

further clearance and has not received holding instructions, 

plan to hold southwest on the 221° radial using left-hand 

turns, as depicted. If this holding pattern is not charted, 

hold west of the VOR on V214 using right-hand turns. 

Where required for aircraft separation, ATC may request 

that the pilot hold at any designated reporting point in a 

2-51 
 

 

 

standard holding pattern at the MEA or the MRA, whichever 

altitude is the higher at locations where a minimum holding 

altitude has not been established. Unplanned holding at 

en route fixes may be expected on airway or route radials, 

bearings, or courses. If the fix is a facility, unplanned 

holding could be on any radial or bearing and there may 

be holding limitations required if standard holding cannot 

be accomplished at the MEA or MRA. 

Maximum Holding Speed 

The size of the holding pattern is directly proportional 

to the speed of the aircraft. In order to limit the amount 

of airspace that must be protected by ATC, maximum 

holding speeds in knots indicated airspeed (KIAS) have 

been designated for specific altitude ranges. [Figure 2-73] 

Even so, some holding patterns may have additional speed 

restrictions to keep faster aircraft from flying out of the 

protected area. If a holding pattern has a nonstandard 

speed restriction, it is depicted by an icon with the limiting 

airspeed. If the holding speed limit is less than the pilot feels 

necessary, advise ATC of the revised holding speed. Also, if 

the indicated airspeed exceeds the applicable maximum 

holding speed, ATC expects the pilot to slow to the speed 

limit within three minutes of the ETA at the holding fix. 

Often pilots can avoid flying a holding pattern, or reduce 

the length of time spent in the holding pattern, by slowing 

down on the way to the holding fix. 

High Performance Holding 

When operating at higher airspeeds, there are certain 

limitations that must be adhered to. For example, aircraft 

do not make standard rate turns in holding patterns if the 

bank angle exceeds 30°. If your aircraft is using a flight 

director system, the bank angle is limited to 25°. The aircraft 

must be traveling over 210 knots true airspeed (TAS) for the 

bank angle in a standard rate turn to exceed 30°; therefore, 

this limit applies to relatively fast aircraft. An aircraft using 

a flight director would have to be holding at more than 

170 knots TAS to come up against the 25° limit. These true 

airspeeds correspond to indicated airspeeds of about 183 

and 156 knots, respectively, at 6,000 feet in a standard 

atmosphere. 

En Route Safety Considerations 

Fuel State Awareness 

In order to increase fuel state awareness, pilots are required 

to monitor the time and fuel remaining during an IFR flight. 

For example, on a flight scheduled for one hour or less, the 

flight crew may record the time and fuel remaining at the 

top of climb (TOC) and at one additional waypoint listed 

in the flight plan. Generally, TOC is used in aircraft with an 

FMS, and represents the point at which cruise altitude is first 

reached. TOC is calculated based on current altitude, climb 

speed, and cruise altitude. The pilot may elect to delete the 

additional waypoint recording requirement if the flight is 

so short that the record will not assist in the management 

of the flight. For flights scheduled for more than one hour, 

the pilot may record the time and fuel remaining shortly 

after TOC and at selected waypoints listed in the flight plan, 

conveniently spaced approximately one hour apart. The 

actual fuel burn is then compared to the planned fuel burn. 

Each fuel tank must be monitored to verify proper burn 

off and appropriate fuel remaining. For two-pilot aircraft, 

the pilot monitoring (PM) keeps the flight plan record. On 

three-pilot aircraft, the second officer and PM coordinate 

recording and keeping the flight plan record. In all cases, 

the crew member(s) making the recording communicates 

the information to the pilot flying. 

Diversion Procedures 

OpSpecs for commercial operators include provisions for en 

route emergency diversion airport requirements. Operators 

are expected to develop a sufficient set of emergency 

diversion airports, so that one or more can be reasonably 

expected to be available in varying weather conditions. 

The flight must be able to make a safe landing, and the 

airplane maneuvered off of the runway at the selected 

diversion airport. In the event of a disabled airplane 

following landing, the capability to move the disabled 

airplane must exist so as not to block the operation of any 

recovery aircraft. In addition, those airports designated 

for use must be capable of protecting the safety of all 

personnel by being able to: 

•	 Offload the passengers and flight crew in a safe 

manner during possible adverse weather conditions. 

•	 Provide for the physiological needs of the passengers 

and flight crew for the duration until safe evacuation. 

•	 Be able to safely extract passengers and flight crew 

as soon as possible. Execution and completion of the 

recovery is expected within 12 to 48 hours following 

diversion. 

Part 91 operators also need to be prepared for a diversion. 

Designation of an alternate on the IFR flight plan is a good 

first step; but changing weather conditions or equipment 

issues may require pilots to consider other options. 

2-52