The Effects of Laser 

Illumination on Operational 

and Visual Performance of 

Pilots During Final Approach

Van B. Nakagawara

Ronald W. Montgomery

Civil Aerospace Medical Institute

Federal Aviation Administration

Oklahoma City, OK 73125

Archie E. Dillard

Flight Technologies and Procedures Division

Federal Aviation Administration

Oklahoma City, OK 73125

Leon N. McLin

Air Force Research Laboratory 

San Antonio, TX 78235

C. William Connor 

SAE G-10 Committee

Melbourne, FL 32951

Civil Aerospace Medical Institute

Federal Aviation Administration

Oklahoma City, OK 73125

June 2004

Final Report

This document is available to the public

through the National Technical Information

Service, Springfield, Virginia 22161.

Office of Aerospace Medicine

Washington, DC 20591

DOT/FAA/AM-04/9
NOTICE

This document is disseminated under the sponsorship of

the U.S. Department of Transportation in the interest of

information exchange. The United States Government

assumes no liability for the contents thereof.
i

Technical Report Documentation Page 

1. Report No. 2. Government Accession No. 3. Recipient's Catalog 

No. 

DOT/FAA/AM-04/9 

4. Title and Subtitle 5. Report Date 

June 2004 

6. Performing 

Organization Code 

The Effects of Laser Illumination on Operational and Visual

Performance of Pilots During Final Approach

7. Author(s) 8. Performing 

Organization Report No. 

Nakagawara VB1, Montgomery RW1, Dillard AE2, McLin LN3, Connor CW4

9. Performing Organization Name and Address 10. Work Unit No. 

(TRAIS) 1

FAA Civil Aerospace Medical Institute, P.O. Box 25082, Oklahoma City, OK 73125 

2

FAA Flight Technologies & Procedures Division, Oklahoma City, OK 73125 

3

US Air Force Research Laboratory, San Antonio, TX 78295 

4

SAE-G-10 Committee, Melbourne, FL 32951 

12. Sponsoring Agency name and Address 13. Type of Report and 

Office of Aerospace Medicine Period Covered 

Federal Aviation Administration 

800 Independence Ave, S.W. 

Washington, DC 20591 14. Sponsoring Agency 

Code 

15. Supplemental Notes 

Work was accomplished under approved task AM-B-03-PRS-94. 

16. Abstract 

INTRODUCTION: Several hundred incidents involving the illumination of aircrew members by laser light have 

been reported in recent years, including several that could have had serious consequences. The purpose of this report 

is to evaluate the performance of pilots exposed to visible laser radiation during final approach maneuvers at 100 feet 

above the runway in the Laser-Free Zone (LFZ). METHODS: Thirty-four pilots served as test subjects for this study. 

Pilot performance was assessed in a Boeing 727-200 Level C flight simulator using four eye-safe levels of visible laser 

light (0, 0.5, 5, and 50 μW/cm2

) during four final approach maneuvers (three 30o left and one 30o right turn to final 

approach). Subjective responses were solicited after each trial and during an exit interview. The pilots were asked to 

rate on a scale from 1 to 5 (1 = none, 2 = slight, 3 = moderate, 4 = great, and 5 = very great) the affect each laser 

exposure had on their ability to operate the aircraft and on their visual performance. The average subjective ratings 

were calculated for each exposure level and flight maneuver, and an analysis of variance (ANOVA) was performed. 

RESULTS: Average subjective ratings for operational and visual performance were 2.93 (Range = 2.35 – 3.29; SD = 

1.37) and 3.16 (Range = 2.56 – 3.62; SD = 1.30), respectively. ANOVA found statistically significant differences (p < 

0.05) between the 0.5 μW/cm2

 operational and visual performance ratings and those for the 5 and 50 μW/cm2

exposures. Approximately 75% of the survey responses indicated that subjects experienced adverse visual effects 

resulting in some degree of operational difficulty when illuminated by low-level laser radiation. CONCLUSION:

This study confirmed that the illumination of flight crewmembers with laser radiation ≥ 0.5 μW/cm2

 is unacceptable 

in the LFZ. Provided the exposure limit established for the LFZ (i.e., 50 nW/cm2

) is not exceeded, a sufficient margin 

of safety appears to exist for protecting pilots from accidental laser exposure during final approach. 

17. Key Words 18. Distribution Statement 

Lasers, Eye, Perception, Performance, Pilots, Vision Document is available to the public through the 

National Technical Information Service; 

Springfield, Virginia 22161 

19. Security Classif. (of this report) 20. Security Classif. (of this page) 21. No. of Pages 22. Price 

Unclassified Unclassified 16

Form DOT F 1700.7 (8-72) Reproduction of completed page authorized

1

THE EFFECTS OF LASER ILLUMINATION ON OPERATIONAL AND VISUAL

PERFORMANCE OF PILOTS DURING FINAL APPROACH

BACKGROUND

In the United States and other developed countries, 

laser (Light Amplification by Stimulated Emission of 

Radiation) devices have become less expensive and more 

commonplace. When used responsibly, lasers have many 

beneficial applications; however, improper or careless use 

of these devices can result in serious hazards for those 

exposed to their radiation. Applications for lasers include 

entertainment equipment (CD and DVD players), supermarket scanners, fiber-optic communication networks, 

handgun and rifle sights, laser pointers for highlighting 

areas of interest during presentations, medical devices, 

and industrial tools. In addition, lasers are frequently 

used outdoors where their tightly collimated beams of 

light are projected into the sky to attract the public or 

provide entertainment in the form of elaborately orchestrated laser lightshows at special events, theme parks, 

and casinos. Other uses for lasers in navigable airspace 

include astronomical and atmospheric research, deepspace communications, orbital satellite imaging, and 

defense systems designed to track, target, and destroy 

military targets (1,2).

Pilots use their eyes to obtain the vast majority of all 

the information needed to safely fly an aircraft. A pilot 

must see well over a range of distances to avoid other 

aircraft in-flight and objects on runways and taxi lanes, 

scan instrument displays, and read maps, charts, and flight 

manifests. Operation of an aircraft at night presents additional visual challenges for the pilot. To ensure optimal 

visual performance at night when viewing objects inside 

and outside the cockpit, a pilot’s eyes should be adapted 

for mesopic vision. Maintaining this mesopic state can 

sometimes be difficult. For instance, prolonged exposure 

to darkness can result in “night myopia” (i.e., the inability 

to see distant objects or fine detail due to the loss of focus 

from over accommodation of the eye). Furthermore, exposure to relatively bright light can result in an inability 

to see well at low-light levels, due to deactivation of the 

eyes’ rod receptors (3). If the eyes are briefly exposed to 

a source of intensely bright light, such as from a laser, 

while in a mesopic state of adaptation, temporary visual 

impairment will almost certainly occur (4). Visual effects 

can last for several seconds to several minutes, and dark 

adaptation may take 30 minutes or longer to be fully 

restored. The three most common physiological effects 

associated with exposure to bright lights are (5):

1. Glare – Obscuration of an object in a person’s field 

of vision due to a bright light source located near the 

same line of sight.

2. Flashblindness – A visual interference effect that persists 

after the source of illumination has been removed.

3. Afterimage – A transient image left in the visual field 

after an exposure to a bright light.

The demands on a pilot’s vision are task dependent 

and frequently change according to the particular phase 

of flight and current visual conditions. Of principal concern to aviators is the possibility of being illuminated 

by a laser during terminal operations, which include 

approach, landing, takeoff, and departure maneuvers. 

Aviators conducting low-level flight operations at night 

are particularly vulnerable to accidental or malicious laser 

illumination. During these activities, the pilot’s visual 

workload is highest, and the time to recover from exposure 

to a visually debilitating light source is minimal. Should 

distractions or physiological impairment disrupt cockpit 

procedures, flight crew coordination, or communication 

between the pilot and air traffic control personnel during critical phases of flight, the consequences could be 

catastrophic.

To minimize distractions and reduce the potential for 

flight procedure errors during approach to landing, the 

Code of Federal Regulations (CFR) Part 121, §542 (6); 

Part 125, §311 (7), Part 135, §100 (8) require a “sterile” 

cockpit (i.e., only operationally relevant communication) 

below 10,000 feet (9). Below 1,000 feet, the aircraft must 

be in a landing configuration and in position to complete 

a normal landing. In order to continue the descent, crewmembers must be able to visually identify the runway 

threshold and/or appropriate lighting configurations. If 

these lighting configurations are not visually identifiable, 

the pilot must execute a go-around (6,7,8,9).

In recent years, the Civil Aerospace Medical Institute’s 

Vision Research Team has compiled a database containing several hundred reports involving laser illumination 

of military and civilian aircraft, including law enforcement and medical evacuation helicopters. Some of these 

incidents have resulted in reports of pilots being startled, 

distracted, temporarily blinded, and disoriented. While 
2 

there have been documented reports of aviation accidents 

associated with glare and flashblindness induced by natural sunlight (10) and exposure to high-intensity artificial 

light sources, such as aircraft landing lights and runway 

approach lights (11,12), no accidents have been attributed 

to the illumination of crewmembers by lasers. However, 

given the considerable number of reported laser incidents 

that have resulted in visual and operational problems, the 

potential for an aviation accident definitely exists. Two 

laser illumination incidents that seriously compromised 

aviation safety are summarized below:

 • At approximately 6:30 pm PST on October 30, 

1995, the first officer on Southwest Airlines flight 

1367 sustained a debilitating eye injury after being 

irradiated by a laser beam on departure from McCarran 

International Airport, Las Vegas, NV. The airplane was 

enroute from Las Vegas to San Antonio, TX, climbing 

through 7,000 feet MSL, on a standard instrument 

departure route when the incident occurred. The 

pilot-in-command (first-officer) reported that the 

laser beam sweep through the cockpit, resulting in 

temporary blindness and pain in his right eye, in addition to after-image effects that impaired the vision 

in his left eye. The pilot could not focus or interpret 

any instrument indications and was disoriented for 

several minutes requiring the captain to assume control 

of the aircraft (13). Note: As a result of this incident, 

the Federal Aviation Administration (FAA) placed a 

moratorium on outdoor laser activities in the Las Vegas 

area.

 • On November 29, 1996, a suspected laser beam 

illuminated a Skywest Airlines pilot during approach 

on flight 5410 into Los Angeles Airport (LAX). 

The Embraer EMB-120 was over a college campus 

on visual approach to LAX from Bakersfield, CA, 

when the incident occurred. The aircraft was on a 

right base leg, level at 6,000 feet MSL, when the 

captain was exposed to a bright light in his right 

eye while looking for downwind traffic through the 

right window. As the flight continued, the captain 

found it increasingly difficult to see because of the 

burning and tearing he was experiencing in that 

eye. On final approach, he relinquished control to 

the co-pilot who completed the landing. Examination revealed the pilot suffered multiple flash burns 

to his right cornea (14). Note: As a result of this 

incident, the National Transportation Safety Board 

(NTSB) recommended the FAA change the existing 

guidelines to protect pilots from temporary visual 

incapacitation and to conduct research to validate 

laser exposure limits.

Initially intended to protect flight-crew personnel 

and passengers from biological tissue damage resulting from accidental exposure to outdoor laser activity, 

FAA Order 7400.2 was originally based on the Food & 

Drug Administration’s (FDA’s) “Performance Standards 

for Light-Emitting Products” (15). This FDA standard 

utilizes the recommended Maximum Permissible Exposure (MPE) of 2.5 milliwatts per centimeter squared 

(mW/cm2) for continuous wave (CW) lasers (16). The 

MPE is used to calculate the Nominal Ocular Hazard 

Distance (NOHD). The NOHD is the distance along 

the axis of a laser beam beyond which an individual may 

be exposed without risk of ocular tissue damage. The 

NTSB recommendation and the increasing number of 

reported laser illumination incidents prompted a study 

to improve aviation safety by limiting acceptable laser 

exposure levels below that which could cause visual 

impairment of flight crewmembers while performing 

critical flight maneuvers.

As a result of the NTSB recommendations and research activities supported by the FAA and the Society 

of Automotive Engineers (SAE) G-10T (Laser Safety 

Hazards Subcommittee), FAA Order 7400.2 (Part 6. 

Miscellaneous Procedures: Outdoor Laser Operations) 

was revised to include new guidelines for Flight Safe 

Exposure Limits (FSELs) in specific zones of navigable 

airspace associated with airport terminal operations. 

This revision was made to augment the existing MPE 

that limited exposure in the Normal Flight Zone below 

that which could cause ocular tissue damage. Based on 

consultations with laser and aviation experts, scientific 

research, and historical safety data, 100 microwatts per 

centimeter squared (μW/cm2) was identified as the level 

of exposure at which significant flashblindness and afterimages could interfere with a pilot’s visual performance. 

Similarly, 5 μW/cm2 was determined to be the level at 

which significant glare problems may occur. When a laser 

is to be operated outdoors in the vicinity of an airport or 

air traffic corridor, the FAA may conduct an aeronautical 

study to identify the zones of airspace around an airport 

or airway that must be protected by the application of the 

appropriate FSEL. These zones and FSELs include:

• Laser Free Zones = 50 nanowatts per centimeter 

squared (nW/cm2),

• Critical Flight Zone = 5 μW/cm2,

• Sensitive Flight Zone = 100 μW/cm2, and

• Normal Flight Zone = 2.5 mW/cm2.

Figure 1 shows a profile view of how the new flight 

zones and FSELs would be applied to a single-runway 

airport. Not depicted in this figure is the Normal Flight 

Zone (NFZ), which would apply to all navigable airspace 

beyond the Sensitive Flight Zone (SFZ). (Note: The SFZ 
3

is optional and may be applied based on the findings 

of the aeronautical study.) The Laser Free Zone (LFZ) 

includes airspace in the immediate proximity of the airport, up to and including 2,000 feet above ground level 

(AGL), extending 2 nautical miles (NM) in all directions 

measured from the runway centerline. Additionally, the 

LFZ includes a 3 NM extension, 2,500 feet each side 

of the extended runway centerline. The Critical Flight 

Zone (CFZ) includes the space outside the LFZ to a 

distance 10 NM from the Airport Reference Point (ARP) 

to 10,000 feet AGL.

Since the September 11, 2001, terrorist attacks on 

the United States, the FAA and other government agencies have become more aware of possible terrorist acts 

involving civil aviation aircraft. Advances in technology 

have increased the portability, output power, and accessibility of laser devices, together with the potential for an 

individual or group of terrorists to interfere with flight 

crewmembers conducting low-altitude maneuvers. A laser 

attack could be quickly deployed and withdrawn, leaving no obvious collateral damage or projectile residue, 

and would be difficult to detect and defend against. The 

possible visual impairment, startle, distraction, and the 

loss of spatial orientation created by such an attack could 

make landing an aircraft difficult at best. A sufficiently 

powerful laser could cause permanent ocular damage, 

blinding crewmembers and make a successful landing 

virtually impossible. While regulations cannot minimize 

the likelihood of a malicious act, research can provide 

insight into the seriousness of the threat and a basis for 

the development of defensive methodologies.

The FAA performed a study in response to an NTSB 

recommendation (17) to investigate the maximum safe 

level of laser light exposure for pilots conducting terminal 

operations. The original study focused attention on the 

CFZ where the majority of accidental laser exposures 

had occurred (18). This study found that the FSEL (5 

μW/cm2) established for the CFZ was adequate for protecting pilots from serious temporary visual impairment. 

However, this research paper reports on ancillary trials 

performed during the original study to investigate laser 

exposures in the Laser-Free Zone. This report evaluates 

the effect that laser exposures have on a pilot’s operational 

and visual performance while conducting short-final maneuvers at 100 feet AGL.

SENSITIVE FLIGHT ZONE

100 μW/cm2

CRITICAL FLIGHT ZONE

5 μW/cm2

LASER FREE FLIGHT ZONE

50 nW/cm2

AIRPORT REFERENCE POINT (ARP)

10 NM 10 NM

TO BE 5 NM 5 NM

DETERMINED

TO BE

DETERMINED

2000 ft 8000 ft TO BE

DETERMINED

Figure 1: Profile view of a single-runway airport and the application of protected flight zones. (Not 

drawn to scale.)
4 

METHODS

To assess the affect of laser light exposure on the operational and visual performance of aviators, the FAA’s 

Boeing 727-200 Level C, full-motion flight simulator at 

the Mike Monroney Aeronautical Center, in Oklahoma 

City, OK, was utilized. Thirty-eight multi-engine-rated 

civilian and military pilots were recruited to serve as human test subjects for this study. Prospective subjects were 

interviewed regarding their ophthalmic medical history. 

Every participant was given a pre-flight ophthalmic exam 

to ensure normal vision and ocular health. Persons reporting a history of eye disease, hypersensitivity to light, 

or taking photosensitizing drugs were not accepted for 

participation in the study. The pre-flight exam included 

fundus photography and visual field testing of both 

eyes. Participants were required to have visual acuity 

correctable to at least 20/20, a normal Amsler grid, and 

no ocular pathology. After completing the test flights, 

visual acuity, fundus photography, and visual field testing were repeated to verify that the subjects sustained 

no lasting adverse effects from the laser exposures. This 

study received Institutional Review Board (IRB) clearance 

before its initiation. All subjects in the study gave their 

voluntary informed consent and were free to withdraw 

at any point during the study.

As in previous human laser experiments, such as those 

conducted at Brooks Air Force Base in San Antonio, TX, 

the laser exposure level did not exceed the MPE for any 

single exposure (19,20). The MPE for direct ocular viewing of a 532 nm laser beam imaged as a point source for 

1 second is 1.8t 0.75 mJ/cm2, where t = seconds, or

MPE = 1.8(1) 0.75 millijoules per centimeter 

 squared (mJ/cm2)

 = 1.8 mJ/cm2.

The highest single planned exposure was 50 μJ/cm2. A 

50 μW/cm2 exposure for 1 second is equal to 50 μJ/cm2, 

or 2.8% of the MPE.

For multiple exposures, the calculation of MPE is 

sometimes more conservative if all exposures delivered 

over a 24-hr period are treated as a single continuous 

exposure. The MPE for an exposure duration between 

18 x 10-6 and 10 seconds is also given by 1.8t 0.75 mJ/cm2. 

The planned cumulative exposure in the LFZ† for each 

subject was 55.5 μJ/cm2 over a total laser exposure time 

of 3 seconds. The MPE for a cumulative exposure of 

3 seconds equals 4.1 mJ/cm2. Therefore, the planned 

cumulative exposure of 55.5 μJ/cm2 delivered to each 

subject was only 1.4% of the MPE.

Four test scenarios were developed, based on the following independent variables:

Laser power levels:

0 μW/cm2,

0.5 μW/cm2 for 1 second,

5.0 μW/cm2 for 1 second, and

50.0 μW/cm2 for 1 second.

Operational maneuver:

Short-final approach – 30o Left turn,

Short-final approach – 30o Right turn.

During the experiment each exposure level was 

presented once, and total simulator time was about 

40 minutes. The independent variables were randomly 

manipulated among the four test scenarios, and all laser 

exposures were 1 second in duration. The four approach 

scenarios included three 30o left turns and one 30o right 

turn. The single zero-level-exposure trial provided the 

subjects with a sense of uncertainty as to whether the laser 

would come on during any given maneuver. Except for 

the zero-level-exposure trials, subjective responses were 

solicited after each trial (see Appendix A) and during an 

exit interview.

A collimated beam of green light with a peak spectral 

irradiance at 532 nm wavelength was generated by a 

continuous-wave (CW) doubled Nd:YAG laser. A fiber 

optic cable was used to deliver the beam to the simulator’s 

visual display array. A 30o cone of diffuse laser light was 

emitted from the fiber optic cable and delivered to the 

subject’s head position. A radiometer was used to measure the irradiance at the subject’s eye. Seat height was 

adjusted for each test subject. Laser exposures were approximately equivalent for the expected variability in eye 

positions between subjects. Exposures occurred following 

a steady-state turn at 100 feet AGL while the aircraft 

was on short-final approach. Subjects were instructed 

to continue normal procedures and fly as efficiently as 

possible during the laser exposure. A certified Laser Safety 

Officer operator was present throughout the experiment 

to ensure that the laser operated safely.

† NOTE: In a similar manner, eight additional approach maneuvers and four takeoff/departure maneuvers were conducted to evaluate the 

test subjects’ reactions to laser illumination within the CFZ. Test subjects were exposed to the three identified laser exposure levels and a zerolevel-exposure on three separate occasions, while on visual and ILS approach and during takeoff/departure maneuvers. Total cumulative exposure for both studies was 222 μJ/cm2

 for 12 seconds, or 2.2% of the MPE. The results from the CFZ investigation were reported in a separate 

paper (18). Only laser exposures within the Laser Free Zone were used in this analysis.
5

A simulation test director was present in the cockpit 

to initiate and monitor each test scenario. In addition, a 

cockpit operator flew as co-pilot and was responsible for 

recording the subject’s responses to a series of questions 

after each test flight. The pilots were asked to rate on a 

scale from 1 to 5 (1 = none, 2 = slight, 3 = moderate, 4 

= great, and 5 = very great) the effect each laser exposure 

had on their ability to operate the aircraft and on their 

visual performance. Subjects were also asked to provide 

any comments relevant to potential exposure-induced 

performance or visual difficulties.

RESULTS

Of the 38 subjects recruited, 34 subjects completed 

all test scenarios. Four recruits were excused from this 

study due to pre-existing conditions (i.e., miotic pupils, 

recent refractive surgery) or eliminated due to problems 

with the laser control program that resulted in corrupted 

data. The average age of the pilots who completed the 

entire study was 40.3 years (standard deviation = 13.45; 

range: 22 to 70 years of age). One subject was female; 

19 subjects used refractive correction (16 spectacle and 

3 contact lens) during the trials.

Figure 2 presents the average of all subjective responses 

to the in-flight questionnaires (see Appendix A) administered to each test subject after laser exposure at 100 feet 

AGL. Subjects rated the laser’s affect on visual performance 

higher than its affect on operational performance for all 

levels of exposure. The average total subjective ratings were 

2.93 and 3.16 for operational and visual performance, 

respectively. ANOVA found both the average operational 

and visual performance ratings increased significantly (p 

< 0.05) between the 0.5 and 5.0 μW/cm2 laser exposure 

levels, while no significance was found between the 5.0 

and 50 μW/cm2 laser exposure levels. The error bars show 

the standard deviations of the ratings. 

Table 1 shows the total frequency of visual effects 

reported by subjects immediately after each exposure. In 

some instances, subjects reported that they experienced a 

combination of two or all three adverse visual effects for 

a particular exposure. Reports of multiple visual effects 

increased as the laser exposure level increased (i.e., 5, 6, 

and 10 multiple reports, for the 0.5, 5.0, and 50 μW/cm2

exposure levels, respectively), as did reports of the more 

severe visual effects (flashblindness and afterimages).

Figure 3 summarizes the percentage of visual effect 

responses solicited from all subjects immediately after 

each exposure. The most common adverse effects reported 

were glare (30.9%) and flashblindness (30.9%), followed 

by afterimage (13.0%). In 25.2% of all the responses, 

test subjects indicated they experienced no adverse visual 

effects when exposed to any of the three levels of laser 

irradiance.

Figure 2: Average subjective rating of pilots’ operational and visual performance by exposure level.

AVERAGE SUBJECTIVE RATING BY EXPOSURE LEVEL

2

3

4

5

Subjective Rating

Operational 2.35 3.15 3.29 2.93

Visual 2.56 3.29 3.62 3.16

0.5 uW/cm2 5.0 uW/cm2 50 uW/cm2 TOTAL
6 

Figure 3: Percentage of adverse visual effects experienced by test subjects for each exposure level.

0.0%

10.0%

20.0%

30.0%

40.0%

PERCENTAGE OF VISUAL EFFECTS

33.3% 20.0% 22.7% 25.2%

35.9% 32.5% 25.0% 30.9%

17.9% 37.5% 36.4% 30.9%

NONE

GLARE

FLASHBLINDNESS

AFTERIMAGE 12.8% 10.0% 15.9% 13.0%

0.5 uW/cm2 5.0 uW/cm2 50 uW/cm2 TOTAL

Table 1: Frequency of visual effects reported by test subjects for each exposure level.

FREQUENCY OF VISUAL EFFECTS BY EXPOSURE LEVEL 

Effects 0.5 μW/cm2

 5.0 μW/cm2 50 μW/cm2 TOTAL 

None 13 8 10 31

Glare 14 13 11 38

Flashblindness 7 15 16 38

Afterimage 5 4 7 16

Total 39 40 44 123
7

After each scenario, the test subjects were asked to 

comment on what affect the laser exposure had on their 

visual and operational capabilities. The figure (see Figure 

4) and text below summarize the subjects’ most frequently 

reported comments for the corresponding level of laser 

exposure.

At the 0.5 μW/cm2 level of exposure, 38% of the 

subjects (n=13) described either being momentarily disturbed, briefly distracted, flashblinded, or loss of depth 

perception, visual contact with the runway surface and/or 

visual clues outside the cockpit. One subject felt the need 

to execute a missed approach or “go around” maneuver 

(i.e., aborted landing = 1, or 3%).

At the 5.0 μW/cm2 level of exposure, 62% of the 

subjects (n=21) reported various effects that included 

momentary flashblindness, losing view of the runway 

surface, loss of depth perception, and/or brief distraction. Of these, four subjects (12%) executed “go around” 

maneuvers, while one subject (3%) relinquished control 

of the aircraft to the co-pilot, and two subjects (6%) 

commented that they would have aborted the landing if 

it were a “real-world” incident (i.e., actual and potential 

aborted landings = 7, or 21%).

At the 50.0 μW/cm2 level of exposure, 56% of the 

subjects (n=19) provided comments regarding the difficulties they experienced, including having to seek shelter 

from the harsh light (ducking under the glare shield), 

momentary flashblindness resulting in the total loss of view 

outside the cockpit, and having to transition to instrument 

flight rules. Of these, four subjects (12%) executed “go 

around” maneuvers, while five subjects (15%) reported 

that they would have performed a missed approach if 

it were a “real-world” incident or if the duration of the 

laser exposure had been longer (i.e., actual and potential 

aborted landings = 9, or 26%).

DISCUSSION

Approximately 75% of the responses solicited from 

subjects indicated they had experienced adverse visual 

effects resulting in some degree of operational difficulty 

when illuminated by eye-safe levels of laser radiation during final approach maneuvers. Even at the lowest level of 

laser exposure (0.5 μW/cm2), two-thirds of the responses 

indicated that subjects experienced glare (36%), flashblindness (18%), and afterimages (13%), at least while 

the laser stimulus was present. These responses and a 

missed approach associated with the lowest level of laser 

exposure in this study confirm that laser illumination of 

flight crewmembers in the LFZ at or above 0.5 μW/cm2

should be avoided. In addition, when illuminated by the 

two higher laser exposure levels (5 and 50 μW/cm2), 

0%

10%

20%

30%

40%

50%

60%

70%

PERCENTAGE OF OPERATIONAL EFFECTS

VARIOUS EFFECTS 38% 62% 56% 52%

ABORTED LANDING 3% 21% 26% 17%

0.5 uW/cm2 5.0 uW/cm2 50 uW/cm2 TOTAL

Figure 4 Figure 4: Percentage of adverse operational effects experienced by test subjects for each exposure level. : Percentage of adverse operational effects experienced by test subjects for each exposure level.
8 

subjects missed eight approaches, relinquished command 

to the co-pilot once, and indicated they had significantly 

(p < 0.05) greater operational and visual performance 

problems compared to the lowest exposure level. The 

FSEL assigned to the LFZ (50 nW/cm2) is one order of 

magnitude below the lowest laser exposure level used in 

these trials (0.5 μW/cm2). While it appears reasonable 

to assume the FSEL established for the LFZ provides an 

adequate margin of safety, that exposure level was not 

evaluated in this study.

The device used to produce the stimulus in this study 

was a commercially available, CW 1-W doubled Nd:

YAG laser, employing multiple filters and a fiber optic 

delivery system that effectively reduced the emitted laser 

radiation to the eye-safe levels. However, even relatively 

low-powered laser devices, such as laser pointers and targeting lasers (used for handgun and rifle sights), could 

be used to deliver irradiance levels that exceed the FSELs 

assigned to the LFZ, CFZ, or even the SFZ. These lasers 

are normally classified Class 3a by the FDA’s Center for 

Devices and Radiological Health (CDRH). Table 2 provides a summary of the primary laser classifications, output 

power limits, and labeling requirements manufacturers 

of laser products must follow in the United States. Strict 

adherence to these regulations is difficult to enforce, and 

some imported devices may exceed the prescribed output 

limits or lack proper labeling.

Several incidents of lasers illuminating aircraft prompted an outright ban of Class 3a (i.e., output power >1 to 

≤ 5 mW) laser pointers in the United Kingdom. One 

incident occurred on October 29, 1997, involving the 

illumination of an Airworld Airbus on final approach to 

Manchester Airport at 600 feet AGL by an individual using 

a laser pointer. The pilot was momentarily distracted but 

managed to safely land the aircraft carrying 180 passengers. 

The pilot reported that if the aircraft had been closer to 

the airport and the laser beam had been shone directly into 

his eyes, the situation could have been very dangerous. 

Furthermore, during this same period, a review conducted 

at Heriot-Watt University in Edinburgh, Scotland, of 17 

laser pointers labeled as Class 2 (i.e., output power ≤ 1 

mW) found that 14 of the devices were actually emitting 

laser energy at the more dangerous Class 3a limit, having 

an output power ≤ 5 mW (21). 

Primarily due to the extended distances between the 

radiation source and those irradiated, the main threat to 

flight crewmembers from accidental or careless exposure 

to low-powered visible lasers is temporary visual impairment, as opposed to eye injury. The minimum distance 

at which a pilot can be exposed to laser radiation without 

experiencing a particular debilitating visual effect is called 

the Minimum Flight Safe Exposure Distance (FSED). 

For visible CW lasers of various output power, the FSED 

can be estimated (see Equation A) by assigning a common beam divergence and exit port diameter (e.g., Φ = 

1 mrad and α = 0.2 cm, respectively), and assuming a 

dark-adapted pupil diameter (0.7 cm) for the exposed 

individual.

Equation A: 2 o

FSEL

P 1.27 1 FSED = −

Table 2: The FDA’s Center for Devices and Radiological Health classification and labeling requirements 

for commercial laser products. 

CLASS 

MAX POWER 

(mW) LOGOTYPE WARNING LABEL 

1 0.39 None Required 

2a > 0.39 to 1 None Required 

(Exposures < 1,000 sec) 

None Required 

2 1 CAUTION Laser Radiation – Do Not Stare into Beam

CAUTION 

(Irradiance < 2.5 mW/cm2

)

Laser Radiation – Do Not Stare into Beam 

or View Directly with Optical Instruments 3a 5 DANGER 

(Irradiance ≥ 2.5 mW/cm2

)

Laser Radiation – Avoid Direct Eye 

Exposure

3b 500 DANGER Laser Radiation – Avoid Direct Exposure 

to Beam

4 > 500 DANGER Laser Radiation – Avoid Eye or Skin 

Exposure to Direct or Scattered Radiation
9

performed to examine the practicality of carrying out 

such attacks on military aircraft (19,20).

Table 3 summarizes the range of distances at which 

the misuse of relatively low-powered lasers (≤ 1 W) could 

present a potential threat to aviation safety in the LFZ 

based on the 50 nW/cm2 FSEL. Similarly, Table 4 provides 

estimated distances within which a more powerful laser 

could disrupt flight crew activities in protected flight 

zones. Attenuation is often ignored in such calculations 

to afford an additional margin of safety. However, it is 

included here to provide a more realistic estimate of the 

potential range a 10-W laser would have in clear air. As 

these estimates indicate, a 10-W laser could present an 

ocular tissue hazard for almost one-half mile and visually 

disrupt flight operations in the LFZ, CFZ, and SFZ over 

considerable distances (i.e., 49.5, 7.18, and 2.03 miles, 

respectively), assuming an adequate aiming mechanism 

was employed.

Ad-hoc analysis using ANOVA was performed to 

compare the performance ratings obtained for the LFZ 

in this study with those of the CFZ collected in the 

previous study where the same test subjects performed 

visual and ILS approach maneuvers (18). Statistically 

significant (p < 0.05) differences were found between the 

operational and visual performance ratings reported at all 

three laser exposure levels. Since the exposure levels were 

the same, and the (approach) maneuvers were similar 

in both studies, this finding suggests that test subjects 

found the visual effects of laser exposure significantly 

more troublesome at 100 feet above the runway than 

they did in the CFZ, where altitude and recovery time 

were more abundant.

Table 3 provides estimates of FSEDs for lasers with 

output powers of Po = 5 mW, 0.5 W and 1 W, at the 

LFZ limit (i.e., 50 nW/cm2) with the estimates adjusted 

for atmospheric attenuation in clear air (i.e., attenuation 

coefficient: μ = 5 X 10-7 cm-1). At long distances, even 

a clear atmosphere will reduce the FSED significantly. 

A simple equation to include atmospheric attenuation 

cannot be found, but the following equation provides a 

conservative estimate.

Where,

r

μ is the distance including atmospheric attenuation

and r

c is the distance calculated from Equation A.

A laser pointer operating at the upper limit of the Class 

3a range (5 mW) would expose a pilot to radiation levels 

above the FSEL established for the LFZ (50 nW/cm2) 

at distances up to 2.03 miles, or 1.77 nautical miles (see 

Table 3). For the more resourceful and malicious individual intent on disturbing normal cockpit activity, that 

distance could be extended to approximately 17 miles 

with a 1-W laser. These estimates illustrate the disruptive 

range of influence that relatively low-powered lasers can 

cause. Targeting flight crewmembers through an aircraft 

windscreen at distances greater than a few hundred yards 

would be difficult without a suitable means for aiming 

the laser, such as a telescopic sight. Studies have been 

Equation B: r 0.5r (1 e ) c −μr

μ = c +

Table 3: Estimated minimum FSEDs for three visible CW lasers at the 

Laser-Free Zone, where FSEL = 50 nW/cm2

. (Note: Estimates are adjusted 

for atmospheric attenuation in clear air: = 5 X 10-7

 cm

-1.) 

Output Power 

Watts 

FSED 

Feet 

FSED 

Miles 

FSED 

Nautical Miles

0.005 10,738 2.03 1.77 

0.5 68,300 12.94 11.24 

1.0 89,327 16.92 14.70 

Table 4: Protected flight zone estimated minimum FSEDs for a visible 10-Watt CW laser. 

(Note: Estimates adjusted for atmospheric attenuation in clear air: = 5 X 10-7

 cm

-1.) 

Flight Zone & 

Exposure Limits 

FSED

Feet 

FSED 

Miles 

FSED

Nautical Miles

LFZ: 50 nW/cm2 261,530 48.5 43.0 

CFZ: 5 uW/cm2 37,938 7.18 6.24 

SFZ: 100 uW/cm2 10,738 2.03 1.77 

NFZ: 2.5 mW/cm2 2,297 0.44 0.38 
10 

In summary, aircraft have been illuminated by laser 

radiation as the result of unintentional carelessness and 

by the malicious acts of individuals. These incidents 

compromise aviation safety due to the distraction and 

temporary visual impairment they often cause for flight 

crewmembers. Laser exposure has proven most disruptive 

when it occurs at low altitude during critical phases of 

flight. This study investigated the performance difficulties 

test subjects experienced when exposed to three eye-safe 

levels of laser radiation on final approach (100 feet AGL) 

in the LFZ. At the lowest exposure level (0.5 μW/cm2), 

67% of the responses indicated that test subjects experienced adverse visual effects from laser exposure, while 

the average subjective ratings were between “slight” and 

“moderate” for both operational and visual performance. 

The two higher exposure levels resulted in significantly 

greater performance difficulties and a total of nine aborted 

landings. These results and the single missed approach 

associated with the lowest exposure level indicate that 

illumination of flight crewmembers by laser radiation at 

or above 0.5 μW/cm2 is unacceptable in the LFZ. The 

exposure limit established for the LFZ (i.e., 50 nW/cm2) 

precludes even 3a laser pointers in this zone. Provided the 

LFZ exposure limit is not exceeded, a sufficient margin of 

safety appears to exist for protecting pilots from accidental 

laser exposure during final approach; however, further 

research may be indicated to confirm this assumption.

REFERENCES

1. Tactical High Energy Laser (THEL) Program. At 

URL: http://www.defense-update.com/directory/

THEL.htm (January 2004).

2. Airborne Laser (ABL) Weapon System. At URL: 

http://www.airbornelaser.com/ (January 2004).

3. Seetharaman V, Motwane S, Athe SM. Correlation 

between dark adaptation and refractive errors. Ind 

J Ophthalmol. Sep-Oct 1985; 33(5):323-25.

4. Florip DJ, Bauer RW. Dark adaptation recovery 

after pulsed light. Ergonomics. Nov 1973; 16(6):

759-64.

5. American National Standards Institute. American 

National Standard for Safe Use of Lasers Outdoors. 

New York, NY. ANSI Z136.6-2000. (2000).

6. Code of Federal Regulations. Title 14, Part 121. 

Washington, DC:U.S. Government Printing Office; December 2004.

7. Code of Federal Regulations. Title 14, Part 125. 

Washington, DC:U.S. Government Printing Office; December 2004.

8. Code of Federal Regulations. Title 14, Part 135. 

Washington, DC:U.S. Government Printing Office; December 2004.

9. U.S. Department of Transportation. Standard operating procedures for flight deck crewmembers. 

AC No. 120-71A. 2/27/2003.

10. Nakagawara VB, Wood KJ, Montgomery RW. 

Natural sunlight and its association to aviation accidents: frequency and prevention. Washington, DC:

Department of Transportation/Federal Aviation Administration; 2003; FAA/Report No. DOT/FAA/

AM-03/6. At URL:http://www.cami.jccbi.gov/

aam-400A/Abstracts/2003TechRep.htm. Available from: National Technical Information Service, 

Springfield, VA 22161. 

11. Nakagawara VB, Montgomery RW, Wood KJ. Aviation accidents and incidents associated with the use 

of ophthalmic devices by civilian pilots. Aviat Space 

Environ Med. Nov 2002; 73(11):1109-13.

12. Nakagawara VB, Wood KJ, Montgomery RW. 

The use of contact lenses by U.S. civilian pilots. 

Optometry. Nov 2002; 73(11):674-84.

13. NTSB Report No. LAX96IA032.

14. NTSB Report No. LAX97IA056.

15. Code of Federal Regulations. Title 21, Volume 8, 

Section 1040.10. Washington, DC:U.S. Government Printing Office; April 2003.

16. American National Standards Institute. American 

National Standard for Safe Use of Lasers. New York, 

NY. ANSI Z136.(1-2000).

17. National Transportation Safety Board. Safety 

Recommendations. Report No. A-97-13, Feb 

26,1997.

18. Nakagawara VB, Montgomery RW, Dillard A, 

McLin L, Connor CW. The effects of laser illumination on operational and visual performance of pilots 

conducting terminal operations. Washington, DC:

Department of Transportation/Federal Aviation Administration; 2003; FAA/Report No. DOT/FAA/

AM-03/12. At URL:http://www.cami.jccbi.gov/

aam-400A/Abstracts/2003TechRep.htm. Available from: National Technical Information Service, 

Springfield, VA 22161. 
11

19. Labo JA, Menendez AR, Allen RG, Edmonds BP, 

Turner MD. Outdoor measures of laser veiling 

glare effects in the visual field: A preliminary study. 

USAFSAM-TP-90-9, USAF School of Aerospace 

Medicine, Human Systems Division (AFSC), 

Brooks AFB, TX. (1990)

20. Varner DC, Cartledge RM, Elliott WR, Menendez 

AR, Carrier R, Richter MJ. Wavelength-dependent 

and -independent effects of veiling glare on the 

visibility of head-up display (HUD) symbology. 

USAFSAM-TR-88-15, USAF School of Aerospace 

Medicine, Human Systems Division (AFSC), 

Brooks AFB, TX. (1988).

21. Rockwell RJ Jr, Ertle WJ, Moss CE. Safety 

recommendations of laser pointers. At URL: 

http://www.rli.com/resources/pointer.asp, January 2004.

A1

APPENDIX A 

In-Flight Questionnaire 

Date: ____________ Subject # ___________ 

These questions are to be asked after each scenario (trial) by either the first officer or simulator operator. Please answer 

the following questions on a scale of 1 to 5 where 1 = ‘none’, 2 = ‘slight’, 3 = ‘moderate’, 4 = ‘great’, and 5 = ‘very great’.

Circle the appropriate number. 

Trial 1: Altitude Readings: Actual __________________ Pilot Response __________________ 

To what extent did the laser exposure affect your... None Slight Moderate Great Very Great 

1. ability to operate the aircraft? 1 2 3 4 5 

Comments: 

2. visual performance? 1 2 3 4 5 

Comments: 

3. What were the visual effects, if any, from the laser exposure? None Glare Flashblindness Afterimage 

Other: 

Trial 2: Altitude Readings: Actual __________________ Pilot Response __________________ 

To what extent did the laser exposure affect your... None Slight Moderate Great Very Great 

1. ability to operate the aircraft? 1 2 3 4 5 

Comments: 

2. visual performance? 1 2 3 4 5 

Comments: 

3. What were the visual effects, if any, from the laser exposure? None Glare Flashblindness Afterimage 

Other: 

Trial 3: Altitude Readings: Actual __________________ Pilot Response __________________ 

To what extent did the laser exposure affect your... None Slight Moderate Great Very Great 

1. ability to operate the aircraft? 1 2 3 4 5 

Comments: 

2. visual performance? 1 2 3 4 5 

Comments: 

3. What were the visual effects, if any, from the laser exposure? None Glare Flashblindness Afterimage 

Other: 

Trial 4: Altitude Readings: Actual __________________ Pilot Response __________________ 
A2

To what extent did the laser exposure affect your... None Slight Moderate Great Very Great 

1. ability to operate the aircraft? 1 2 3 4 5 

Comments: 

2. visual performance? 1 2 3 4 5 

Comments: 

3. What were the visual effects, if any, from the laser exposure? None Glare Flashblindness Afterimage 

Other: