FAA-AM-80-14 

STRESS, ANXIETY, AND THE 

AIR TRAFFIC CONTROL SPECIALIST: 

SOME CONCLUSIONS FROM A 

DECADE OF RESEARCH 

SEPTEMBER 1980 

U.S. DEPARTMENT OF TRANSPORTATION 

FEDERAL AVIATION ADMINISTRATION 

MIKE MONRONEY AERONAUTICAL CENTER 

OFFICE OF AVIATION MEDICINE 
FAA-AM-80-14 

STRESS, ANXIETY, AND THE AIR TRAFFIC CONTROL SPECIALIST: 

SOME CONCLUSIONS FROM A DECADE OF RESEARCH 

Roger C. Smith 

Civil Aeromedical Institute 

Federal Aviation Administration 

Oklahoma City, Oklahoma 

September 1980 

Document is available to the public through the 

National Technical Information Service, 

Springfield, Virginia 22161 

Prepared for 

U.S. DEPARTMENT OF TRANSPORTATION 

Federal Aviation Administration 

Office of Aviation Medicine 

Washington, D.C. 20591 
1. Report No. 2 . Government Accession No. 

FAA-AM-80-14 

4. Title and Subti.tle 

Stress, Anxiety, and the Air Traffic Control 

Specialist: Some Conclusions From a Decade 

of Research 

Technical Report Documentation Page 

3. Recipient's Catalog No. 

5. R~port Dot~ 

~eptemoer 19RO 

6. Performing Organization Code 

f--=--..,....__,...,,--------------------------l 8 . Performing Organ i zotion Report No . 

7 . Authorl s) 

Roger C. Smith 

9, Performing Orgoni zotion Nome and Address 

FAA Civil Aeromedical Institute 

P.O. Box 25082 

Oklahoma City, Oklahoma 73125 

10 . Work Unit No . (TRAIS) 

11 . Contract or Grant No . 

13. Type of Report and Period Covered 

~--------------- 12. Sponsoring Agency Nome and Address --------~ 

Office of Av1ation Medicine 

Federal Aviation Administration 

800 Independence Avenue, SW. 

Washington, D. C. 20591 

15. Supp Iemen tory Notes 

14. Sponsoring Agency Code 

This report was prepared under tasks AM-C-80-PSY-74 and AM-C-80-PSY-79. 

16. Abstract 

It is often assumed that air traffic control specialists (ATCSs) endure a high degree 

of work-related stress and that they may be near the limits of their ability to cope 

with such stress. This paper summarizes a decade of research evaluating possible 

stress effects of work on ATCSs. Studies were conducted at a variety of large and 

small air traffic facilities. A visit of several days to each facility was part ofan 

interdisciplinary research effort involving physiological and biochemical, as well as 

psychological,assessments. The principal psychological measure was the State-Trait 

Anxiety Inventory (STAI). The STAI and other questionnaires were administered at the 

beginning and end of three to five different work shifts scheduled at a facility. The 

findings showed that controller groups scored significantly below college student 

norms on both the A-state (current anxiety level) and A-trait (anxiety proneness) 

measures of the STAI. Results with mood adjective checklists were similar. The findings also showed that anxiety levels (i) increased across an R-hr work shift and (ii) 

were higher on shifts rated ''difficult" than they were on "easy" shifts. 

The establishment of adult norms for the STAI was undertaken to provide a better 

comparison for ATCS data. Results of those efforts indicated that ATCSs had lower 

anxiety scores than the normal adult population. Moreover, A-state scores increased 

from the beginning to end of work shifts for employees in a variety ofnon-air-traffic 

jobs (e.g., engineers), just as they did for ATCSs. Thus, ATCSs are well within 

normal limits on every indicator of psychological states used in these studies and 

appear to experience less anxiety than is the average in other work settings. 

17. Key Words 

Anxiety 

Air Traffic Controllers 

Stress 

Workload 

Shift Work 

19. Security Classif. (of this report) 

Unclassified 

Form DOT F 1700.7 <8-72) 

18. Distribution Statement 

Document is available to the public 

through the National Technical Information 

Service, Springfield, Virginia 22161 

20. Security Clossi f. (of this page) 21. No. of Pages 22. Price 

Unclassified 15 

Reproduction of completed page outhori zed 
STRESS, ANXIETY, AND THE AIR TRAFFIC CONTROL SPECIALIST: 

SOME CONCLUSIONS FROM A DECADE OF RESEARCH 

I. Introduction. 

When stressful occupations are discussed, particularly in the popular press, it 

is common for the air traffic control specialist (ATCS) to be identified as belonging to a professional group under intense stress (9,23). As one author put it: 

"The job of juggling airliners and making snap decisions on which lives depend 

exacts a steep toll in stress-related diseases, nightmares, and acute anxiety" 

(26). In a recent book on occupational stress, Kasl (22) notes that air traffic 

control work is one of those vocations that seems intuitively to be stressful. 

This paper reviews a series of field studies conducted with ATCSs to assess 

possible stress effects in their work. The studies are presented in chronological 

order to provide some indication of how results from one investigation influencerl 

the conduct of the next one. The presentation is also designed to show the development of the perspectives needed to assess most properly the presence or absence of 

work stress in this occupation. 

Attempts to document the presence of unusual stress in the air traffic setting 

date from the middle 1960's (10,11,17); however, concerted efforts to study this 

issue did not get underway until the last part of that decade. The Civil Aeromedical Institute (CAMI) began its program of stress research in 1968, an effort 

which continued throughout the 1970's. 

II. Procedure. 

Most of the CAM! studies were multi disciplinary in scope and i nvo 1 ved psychological, physiological, and biochemical assessments of the state of the ATCS. The 

format of these studies followe·d the same general pattern in each investigation. 

Volunteers were solicited from the crews working at each facility with the understanding that they would be involved with the project for up to 10 days. For the 

psychological portion of the studies, each participant filled out one or more 

assessment questionnaires at the beginning and again at the end of each work shift 

under consideration. The questionnaires varied across studies and each will be 

discussed in the context of the specific study in which it was used. The major 

physiological measure, heart rate, was recorded throughout the work shifts under 

investigation by the use of miniature tape recorders. These instruments permitted 

the participants to remain ambulatory throughout the work shift while providing 

continuous electrocardiographic (ECG) recordings. On occasion, blood pressure and 

the galvanic skin response were also measured. The biochemical measures were 

derived primarily from urine samples collected before, during, and after the work 

shifts under consideration . In some of the earlier CAM! studies there was also 

collection of blood samples after at least one work shift. Since the concern of 

the author in these studies was with the psychological domain, that will be the main 

focus of this paper; however, the physiological findings from the studies will be 

highlighted as well. 

1 
{again biomedical observers) contributed both psychological and physiological/ 

biochemical measurements. 

A total of 16 ATCSs and 4 biomedical observers completed the research tasks. 

The data from the CMACL indicated that, as a group, the Houston ATCSs showed the 

same general pattern as the O'Hare controllers. Scores related to fatigue were 

higher at the end of shifts than at the beginning and were higher for night than 

day shifts. The trend for anxiety indicators in the CMACL to be higher at the end 

of work shifts than at the beginning was also found but was not as pronounced as in 

the O'Hare study. 

Compared to the control subjects who had observed them, Houston ATCSs were less 

fatigued, more vigorous, and less anxious. The comparisons with ATCSs at Chic~go's 

O'Hare International Airport showed the overall degree of positive affect to be 

somewhat higher in Houston. However, most of this effect was due to the difference 

in scores between the day shift measures at Houston and the evening shift measures 

at O'Hare, especially on scales related to fatigue. On the night shifts, the 

situation was reversed, with the O'Hare ATCSs showing the lesser feelings of 

fatigue even though they were considerably busier during this shift than were the 

Houston ATCSs. 

The STAI scores followed the trend of the CMACL data in that scores on the 

A-state scale increased significantly from before to after work on both day and 

night shifts. The use of the STAI also permitted comparison to normative groups, 

whereas this was not possible with the CMACL. The normative group most closely 

matching the air traffic sample was that of college undergraduates who had the 

lowest mean score of any of the available normative groups (high school students, 

surgical patients, prisoners). According to the college student norms, the mean 

A-state score for the Houston ATCSs was at the 42nd percentile. The A-trait scale 

(anxiety proneness) was at the 24th percentile. These findings tenned to affirm the 

CMACL results that the expressed levels of anxiety reported by ATCSs were certainly 

within normal limits and were at relcttively low levels. These data are inconsistent 

with the presence of any unusual emotional stressors. 

Physiological measures showed that heart rates were generally higher during the 

day shift than during the night shift for the Houston ATCSs. The heart rates of 

Houston ATCSs during the day shift were lower than the heart rates obtained from 

evening shifts at O'Hare. The night shifts did not differ. Preshift measures of 

heart rate also showed that the ATCSs at O'Hare had the higher mean rate. This 

suggests that some of the differences observed between these two facilities may 

relate to different baseline levels of physiological arousal rather than to 

differences in the work situation itself. 

The urine analyses for Houston ATCSs showed epinephrine and norepinephrine to be 

higher during day shifts than during night shifts. The comparison with O'Hare ATCSs 

showed that the two facilities differed primarily on night shift measures where 

the greater workload at O'Hare is reflected in the higher level of catecholamine 

excretion. Plasma phosolipids were also found to be higher for O'Hare than for 

Houston ATCSs. 

3 
Study VI. Air Traffic Work Demands and STAI Scores: A Sensitive Measure. At 

this point the psychological data seemed clearly to contradict the notion that 

significant psychological or emotional stress was a factor in air traffic work. 

However, limitations in the design of the previous studies, often due to real-world 

situational and administrative constraints, left many questions unanswered. One of 

these was the question of the sensitivity of the measures, particularly the STAI, 

to stress in the air traffic situation. To answer this question comparisons were 

made of the STAI data from the Houston ATCSs with data from a total of 62 adrlitional 

ATCSs from (i) an extremely busy general aviation tower (Opa Locka, Florirla, a 

nonradar tower primarily serving light and business aircraft) and (ii) an air route 

traffic control center (ARTCC), a radar facility controlling high-altitude 

cross-country traffic (48). Ratings of the difficulty of each day or night of work 

were also obtained. The A-state score was found to increase over twice as much 

across shifts rated "difficult" as for shifts rated "easy." Thus, it appears that 

the STAI was in fact sensitive to variations in arousal associated with perceived 

changes in demand or difficulty. 

The physiological and biochemical measures showed personnel at the general 

aviation tower to be under greater physiological arousal during work than were 

personnel at the ARTCC or the Houston tower, and at about an equal level of arousal 

with the O'Hare ATCSs (35). 

Study VII. Validation of Findings From Houston. The next study was designed to 

replicate and clarify findings from the two studies comparing shift rotation 

schedules at the Houston ~ower (31). The earlier comparisons of the two schedules, 

the 5-day and 2-2-1, at the Houston facility had been hampered by a variety of 

problems, including the fact that no assessment of evening shifts was available for 

the 5-day schedule. This new study was conducted at two large ARTCCs, one on the 

5-day and the other on the 2-2-1 schedule, and covered all shifts at each facility. 

The findings from the STAI in this study again showed (i) no difference in shift 

schedules, (ii) low A-trait and A-state scores compared to scores of college 

students, and (iii) the significant increase in A-state from the beginning to the 

end of work. The biochemical assessment (only biochemical measures were taken in 

this study) appeared to favor the 2-2-1 schedule to some degree, although no 

impressive differences were found. 

Study VIII. Some Effects of Automation on ATCS Stress Indicators. About this 

time, the middle 1970's, computer assistance for ATCSs was beginning to be a factor 

in the air traffic work situation. The system being brought on-line was designed 

to enhance radar targets and to handle information concerning aircraft that up 

until then was either committed to memory or noted by hand. The ATCS remained the 

decision maker but now possessed a rather sophisticated memory aid. In order to 

assess the impact of the introduction of the new computer systems on ATCSs, a CAMI 

research team visited two busy terminal radar facilities (Los Angeles and Oakland, 

California) on the west coast of the United States (30). Data were first collected 

before the installation of the new computer systems, then again some 5 months after 

the systems were in full operation. There were no differences in the psychological 

measures (STAI) taken before and after installation of the computers. Surprisingly, 

the biochemical indices showed several statistically significant increases after the 

installation of the computer systems, primarily in catecholamine excretion. However, 

5 
TABLE 1. STAI (Form Y) Means and Standard Deviations For Normal 

Age: 25 - 29 30 -34 35 - 39 40 - 44 45 - 49 50 - 54 

Sex: M F M F M F M F M F M F 

A-trait· 

Mean 36.6 39.4 34.8 35.7 35.2 34. 8 34.9 36.0 35.3 33.7 34.2 32.4 

SD 10.3 11.4 9.2 8.9 9.3 9.1 8.7 8.7 9.2 9.4 9.0 7.5 

N 57 46 147 61 192 68 260 80 307 55 197 50 

A-state 

Mean 36.8 39.5 36.1 35.0 36.2 36.4 35.6 36.3 36.5 35.9 34.6 32.6 

so 9.6 12.1 10.5 10.0 9.7 11.7 9.9 10.5 11.0 11.9 10.1 7.3 

N 57 46 147 62 193 69 259 80 305 55 199 50 

......... 

TABLE 2. STAI A-trait and A-state Scale Means and Standard Deviations (SD

ATCS Instructors, Non-ATCS Adult Men, and Male College Undergrad

A- TRAIT A-STATE 

Group N Mean so Mean S

ATCSs 198 30.3 6.6 31.1 7

Instructors 92 32. 8 8.9 33. 8 10

Non-ATCSs 1,303 35. 8 10.4 35.1 9

College Undergraduatesa 253 37.7 9.7 36.4 9

aTaken from Spielberger et al. n(51) 
mood self-ratings were lower, at the end than at the beginning of work. Hibler (18) 

expanded upon CAMI studies of shift difficulty and anxiety (48) to include ratings 

by military ATCSs of difficulty and anxiety during shifts, and confirmed that 

A-state levels were higher for difficult shifts and that A-state scores generally 

increased across shifts. The mean A-trait and A-state scores for the military ATCSs 

were similar to those obtained in CAM! studies of civilian ATCSs. In another study, 

Caplan, Cobb, French, Harrison, and Pinneau (3) found anxiety levels among a group 

of midwestern ATCSs to be intermediate in comparison to 22 other occupations. Rose, 

Jenkins, and Hurst (38) reported that more than 80 percent of a group of ATCSs 

participating in an evaluation of health change scored low (over one standard deviation below the mean for college students) on the Tension/Anxiety Scale of the Profile of MOod States (28). Thus, those researchers who have made comparable measures 

of psychological states have obtained results highly consistent with CAMI findings. 

Related work in the physiological area has been limited to two main studies. 

Schad, Gilgen, and Grandjean (39) found that six Swiss ATCSs excreted higher levels 

of catecholamines while doing air traffic work than when providing general supervision or doing clerical work. Rose et al. (38) considered heart rate and blood 

pressure in their health change study. The heart rate values they obtained from 

ATCSs in the northeastern region of the United States tended to be lower than the 

rates obtained from both the O'Hare (33) and Houston (29) studies. On the other 

hand, the mean blood pressures obtained by Rose et al. were considerably higher than 

those obtained at O'Hare. The meaning of these differences in physiological/ 

biochemical findings is not readily apparent. 

Though not directly comparable to CAMI research, there have been other investigations of the health consequences of air traffic work that have implications for 

the assessment of stress in ATCSs . The findings from these studies have been mixed. 

Two studies, by Cobb and Rose (8) and Rose et al. (38), suggest that ATCSs are at 

higher risk than men-in-general for hypertension; however, Booze (1) found hypertensive diagnoses to be well below expectancy in a review of health records for 

25,000 ATCSs. Dougherty (10) found no difference between ATCSs and non-ATCSs in the 

prevalence of ECG abnormality. The evidence that the air traffic system is an 

"ulcer factory" {26) is also equivocal. l))ugherty, Trites, and Dille (11) and 

Hauty, Trites, and Berkley (17) found a higher incidence of self-reported gastrointestinal symptoms by ATCSs than by non-ATCS personnel. The Cobb and Rose (8) and 

Rose et al. (38) studies both reported higher than expected incidence of ulcers in 

their samples of ATCSs. However, Singal, Smith, Hurrell, Bender, Kramkowski, and 

Salisbury (40) found no evidence that ulcers were above expectancy at the O'Hare 

facility, nor did Booze (1) in his survey of medical records from ATCSs. Neuropsychiatric problems were commonly reported in both the Rose et al. (38) and Booze 

(1) studies. However, it was not possible to determine (i) if the rates were above 

expectancy in the Rose et al. study because of the lack of comparable norms, or 

(ii) if the high rate in the survey by Booze occurred only after introduction of a 

special benefits program for ATCSs who were separated from their work for medical or 

administrative reasons. Reaching a general conclusion about these diverse results 

is difficult; perhaps they are best summarized as suggesting that some ATCSs at some 

air traffic facilities may be at higher risk for health change, particularly 

cardiovascular problems, but this is probably not true for the ATCS work force in 

general. 

9 
factors: intelligence, group-conformity, tough-mindedness, and compulsivity (21, 

38,44). In comparison, airline pilots differ substantially from men-in-general on 

11 of the 16PF scales. ATCSs score within the normal range on all scales of the 

California Personality Inventory with relative elevations on the factors associated 

with dominance and relatively lower scores on factors measuring mature socialization 

and respect for authority (38,54). On the Strong Vocational Inventory Blank (2), 

ATCSs score like men-in-general on all but a few scales mostly concerned with 

technical supervisors (45). These findings suggest that ATCSs form a unique occupational group only on a few personality dimensions. However, it is possible that 

those dimensions may be related to their psychological and physiological responses 

to air traffic work. · Rose et al. (38) did find that ATCSs who were Type B 

personalities seemed at higher risk for hypertension than were those who were more 

competitive, an interesting reversal of the usual sort of findings (20). The 

problem is to discern to what extent the incidence of hypertension or other 

physical or psychological problems results from the work, not the person. In other 

words, it is quite ppssible that ATCSs who contract hypertension or other problems 

may be 1 ikely to do so in any work circumstance. Only the development of carefully 

matched control groups can resolve this question. 

Although the problems just discussed require further research, it is clear from 

presently available evidence that the ATCSs appear remarkably free of emotional 

distress. According to Spielberger's (52) process theory of anxiety, this means 

that ATCSs perceive little, if any, threat in their work or the r~sponsibilities 

associated with that work. The physiological data obtained in ATCS re~earch suggest 

normal physiological responses to varied workloads. The extent to which high 

workloads are related to negative consequences for ATCSs is uncertain. There is 

some evidence (19) linking increased physiological responsiveness with cardiovascular and gastrointestinal problems; however, the extent to which this correlation 

is a function of the individual's response style as opposed to the effects of workload or other aspects of the work itself has not yet been determined. According to 

Rose et al. (38), the types of health change data that they obtained are suggestive 

of an interaction between individual predispositions to certain disorders and 

characteristics of the work setting. They suggest that it is not the work itself, 

but the context in which the work is conducted, that is the important factor 

interacting with predisposing factors in the. individual ATCS. 

In conclusion, there is little evidence to support the notion that ATCSs are 

engaged in an unusually stressful occupation. This is not to say that ATCSs never 

encounter unusual stress on the job; however, it does appear that this is the exception rather than the rule. ATCSs appear both well qualified and well suiterl for air 

traffic work. The demands of air traffic work do not appear to place unusual stress 

on ATCSs; this professional group appears quite capable of handling requirements of 

the job without distress. The notion that this occupational group is being pressed 

to the psychological and physiological limit is clearly unjustified. 

1 1 
14. Grandjean, E., G. Wotzka, and H. Kretzschmar: 

tions Into Professional Stress on Air Traffic 

Zurich-Kloten, and Geneva-Cointrin Airports. 

Confederate Co 11 ege of Techno 1 ogy, 1968. 

Psychophysiologic InvestigaControl Officers at the 

Unpublished manuscript, Swiss 

15. Hale, H. B., E. W. Williams, B. N. Smith, and C. E. Melton, Jr.: Excretion 

Patterns of Air Traffic Controllers. AEROSPACE MEDICINE, 42:127-138, 1971. 

16. Harrington, J. M.: Shift Work and Health. London: University of London, ~ondon School of Hygiene and Tropical Medicine, 1978. 

17. Hauty, G. T., D. K. Trites, and W. J. Berkley: Biomedical Survey of ATC 

Facilities. 2. Experience and Age. FAA Office of Aviation ~1edicine Report 

No. AM-65-6, 1965. 

18. ·Hibler, N. S.: The Effects of Stress on State Anxiety in Air Traffic 

Controllers. Doctoral dissertation, University of South Florida, DISSERTATION 

ABSTRACTS INTERNATIONAL, 38:6155-B, 1978. 

19. Higgins, E. A., M. T. Lategola, and C. E. Melton: Three Reports Relevant to 

Stress in Aviati.on Personnel. FAA Office of Aviation ~1edicine Report No. 

AM-78- 5, 1978. 

20. Jenkins, C. D., S. J. Zyanski, and R. H. Rosenman: Coronary-Prone Behavior: 

One Pattern or Several? PSYCHOSOMATIC MEDICINE, 40:25-43, 1978. 

21. Karson, S., and J. W. 0' Dell: Personality Makeup of the American Air Traffic 

Controller. AEROSPACE MEDIClNE, 45:1001-1007, 1974. 

22. Kasl, S. V.: Epidemiological Contributions to the Study of Work Stress. In 

C. L. Cooper and R. Payne (Eds. ), Stress at Work. New York: Wiley and Sons, 

1978. 

23. Lehmann, P.: Job Stress: Hidden Hazard. JOB SAFETY AND HEALTH, 2:4-10, 1974. 

24. Levitt, E. E.: The Psychology of Anxiety. New York: Brooks-Merrill, 1967. 

25. Malmstrom, E. J.: Composite t>bod Adjective Check List. Unpublished manuscript, 

Department of Psychology, University of California, Los Angeles, 1968. 

26. Martindale, D.: Sweaty Palms in the Control Tower. PSYCHOLOGY TODAY, 

10:71-75, 1977. 

27. McKenzie, J. M., P. R. Fowler, R. Moses, and M. J. Burr: Evaluation of Stress 

in Air Traffic Controllers: FAA Academy Instructors. Preprints of the 1977 

Annual Scientific Meetin of the Aeros ace Medical Association, Washington, 

D.C., 99-100, 1977 Summary . 

28. McNair, D. M., M. Lorr, and L. F. Droppleman: Profile of Mood-States: 

Manual. San Diego, California: Educational and Industrial Testing Service, 

1971. 

13 
42. Smith, R. C.: Comparison of the Job Attitudes of Personnel in Three Alr 

Traffic Control Specialties. AEROSPACE MEDICINE, 44:918-927, 1973. 

43. Smith, R. C.: Response Bias in the State-Trait Anxiety Inventory: Detecting 

the Exaggeration of Stress. JOURNAL OF PSYCHOLOGY, 86:241-246, 1974. 

44. Smith, R. C.: A Realistic View of the People in Air Traffic Control. FAA 

Office of Aviation Medicine Report No. AM-74-12, 1974. 

45. Smith, R. C.: Vocational Interests of Air Traffic Control Personnel. 

AEROSPACE MEDICINE, 46:871-877, 1975. 

46. Smith, R. C., B. B. Cobb, and W. E. Collins: Attitudes and Motivations of Air 

Traffic Controllers in Terminal Areas. AEROSPACE MEDICINE, 43:1-5, 1972. 

47. Smith, R. C., and G. L. Hutto: Does Air Traffic Control Work Lead to Psychological Arousal? A Comparison of Air Traffic and Non-Air-Traffic Employees 

Within the FAA. Pre rints of the 1980 Annual Meetin of the Aeros ace Medical 

Association, Washington, D.C., 50-51, 1980 Summary . 

48. Smith, R. C., and C. E. Melton: Susceptibility to Anxiety and Shift Difficulty 

as Determinants of State Anxiety in Air Traffic Controllers. AEROSPACE 

MEDICINE, 45:599-601, 1975. 

49. Smith, R. C., and C. E. Melton: Effects of Ground Trainer Use on the Anxiety 

of Students in Private Pilot Training. AVIATION, SPACE, AND ENVIRONMENTAL 

MEDICINE, 49:406-408, 1978. 

50. Smith, R. C., C. E. Melton, and J. M. McKenzie: Affect Adjective Check List 

Assessment of Mood Variations in Air Traffic Controllers. AEROSPACE MEDICINE, 

42:1060-1064, 1971. 

51. Spielberger, C. D., R. L. Gorsuch, and R. F. Lushene: Manual for the StateTrait Anxiety Inventory. Palo Alto, California: Consulting Psychologists 

Press, 1970. 

52. Spielberger, C. D.: Anxiety as an Emotional State. In C. D. Spielberger (Ed.)

Anxiety: Current Trends in Theory and Research. New York: Academic Press, 

1972. 

53. Trites, D. K.: Problems in Air Traffic Management: VI. Interaction of 

Training Entry Age With Intellectual and Personality Characteristics of Air 

Traffic Control Specialists. FAA Office of Aviation Medicine Report No. 

AM-65-21, 1965. 

54. Trites, D. K., A. Kurek, and B. B. Cobb: Personality and Achievement of Air 

Traffic Controllers. AEROSPACE MEDICINE, 38:1145-1150, 1967. 

55. Zuckerman, M. : The Development of an Affect Adjective Checklist for the 

Measurement of Anxiety. JOURNAL OF CONSULTING PSYCHOLOGY, 24:457-462 , 1960. 

US GOVERNMENT Pf.INTING O>FICE l'l!IO - 341 - 428/378 15