1 Background

This briefing note suggests topics and strategies that can be effective when training flight crews about coping with fatigue related to jet lag. The primary focus is on helping crews learn how to limit sleep loss before return flights in eastward and westward rotations that include a layover. The briefing note provides an overview of key factors that influence jet lag and offers recommendations for training on:

• How to deal with jet lag and limit sleep loss before the return flight
• Sleep and nap management during the layover for eastward and westward rotations

2 Introduction

It is important for flight crews to understand the causes of jet lag and the subsequent performance issues related to it. Aviation training should emphasize that jet lag is a combination of symptoms caused by rapidly traversing across time zones. Crews should understand that jet lag is more than just fatigue. Besides fatigue, symptoms include sleepiness, digestive upsets, impaired judgement, impaired decision making, memory lapses, irritability and apathy.

Trainees should have a good understanding of the fact that each person has an internal body clock that schedules when sleeping, waking and hunger should occur within a 24-hour period. It is important for a trainee to understand that when traveling across several time zones, the day actually becomes longer or shorter than 24 hours because of time changes. Jet lag is the body’s reaction because it cannot adjust the normal body rhythms quickly to the shorter or longer day. The body needs anywhere from a few days to a few weeks to acclimate to the new time zone, or approximately one day for each hour of time zone change.

Training should incorporate the idea that jet lag is not the same for all travel situations. Traveling eastward, which shortens the day, is more difficult than flying westward, which lengthens it. This is because it is much easier for a person to stay awake later (as needed for westward flight) than it is to go to bed early (as needed for eastward flight). Once a crewmember has arrived at the layover destination, how much he or she adjusts to local time depends on the number of local nights during the layover. Training should use the information below and have trainees practice calculating the number of days needed to adjust to local time and when to use the various strategies to avoid jet lag and its related symptoms.

3 Data

A trainee needs to understand how the number of time zones crossed and the direction of travel affect the biological clock. Information covered in training should focus on how the extent of the shift between the biological night and the local night plays an important role in determining layover sleep and nap management. Four categories have been created based on the direction of flight and the number of time zones crossed (TZC) during the flight. These include:

• North-south rotations (NSR): 0 to ±3 time zone differences.
• Westward rotations (WR): Base Time - 4 ≤ TZC ≤ Base Time - 9. In westward rotations, the base time biological night occurs during the end of the afternoon, evening and first half of the night local time.
• Eastward rotations (ER): Base Time + 4 ≤ TZC ≤ Base Time + 9. For +4 and +6 time zone changes in eastward rotations, the base time biological night occurs during the second half of the local night and early in the local morning. For +7 and +9 time zone changes in eastward rotations, the base time biological night occurs during the local morning and afternoon. Thus, the recommendations listed in the following sections below are slightly different for these time zone categories.
• Very high number of time zones crossed (WER): Base Time +10 ≤ TZC ≤ Base Time +12. These time zone changes produce approximately the same shift between the base time biological night and the local night, irrespective of the direction of the flight.

Understanding these time shifts and how they relate to normal base time and local time sleep schedules is very important to prevent jet lag.

4 Recommendations

A flight crewmember should know the advantages or disadvantages of taking his or her main sleep on base time or local time. The following information is designed to help trainees avoid, or minimize, sleep deprivation prior to the return flight. Depending on the timing of the return flight, the recommendations will favor layover or base time rest and activity management. In some cases, particularly when the return flight includes either a local or base night, pilots can choose between which sleep and nap strategies they would like to use based on the relative advantages and disadvantages of each.

• The advantages of taking the main sleep during normal base nighttime hours include good sleep, no biological clock troubles and rapid recovery after rotation. The primary drawback is that sleeping during these hours will affect social interactions during the layover.
• The primary advantage of taking the main sleep during layover nighttime hours is that it is convenient for social life during the layover. Drawbacks include poor sleep, biological clock disturbances and taking longer to recover from the rotation.
• If a crewmember chooses to split sleep into two periods, one during base nighttime and the other during layover nighttime hours, the advantages are that getting some sleep during base nighttime hours should stabilize the biological clock and allow for rapid recovery after the rotation.

Trainees should understand that they must decide which strategy they prefer to adopt based on the duration of the layover in terms of the number of local nights and the number of time zones crossed (see Figure 1).

 

Figure 1: Layover Recommendation Principles

Specific factors to be considered include:

• A high number of nights during the layover and a low number of time zones crossed tend to encourage adjustment of the biological clock to local time. A crewmember should favor local time for rest and activities.
• A low number of nights during the layover and a high number of time zones crossed lend themselves to favoring base time. A crewmember should attempt to prevent adjustment to the local time by favoring base time for rest and activities or by splitting sleep into two periods, one corresponding to base nighttime and the other to local nighttime.
• For the conditions in between, the crewmember must decide whether to try to adjust to local time. Choices should be based on experience and subjective feelings (depending on the ease with which a person can adjust and what he or she prefers to do during the layover).

Trainees should practice using the The Layover Assessment Adjustment Questionnaire (LAAQ) included in the OGHFA materials to help determine adjustment to local time.

Recommendations for the return flight are based on the extent to which each individual crewmember has adjusted to local time. More details on the precise recommendations for the return flight are in the associated checklists referenced below.

5 Key Points

Training should emphasize the role of the biological clock as it relates to jet lag and its symptoms

• Trainees should understand that when they travel across several time zones, the day actually becomes longer or shorter than 24 hours because of time changes
  • Traveling east makes the day shorter, and adjustment is difficult
  • Traveling west makes the day longer, and adjustment is fairly easy
• Trainees should understand whether to adjust sleep and activities to local time during the layover based on:
  • Number of time zones crossed
  • Layover duration
  • Timing of the return flight
• Personal preferences
• Trainees should practice using the LAAQ and other OGHFA materials to assist them in their decisions relating to sleep and fatigue

6 Associated OGHFA Material

• Body Clock Questionnaire
• Circadian Rhythms
• Fatigue Manifestations
• Layover Assessment Adjustment Questionnaire
• Sleep

7 Additional Reading Material

1. Bourgeois-Bougrine, S.; Cabon, P.; Gounelle, C.; Mollard, R.; Coblentz, A.; Speyer, J.J. “Fatigue in Aviation: Point of View of French Pilots.” Aviation Space and Environmental Medicine, 2003.
2. Cabon, P.; Coblentz, A.: Mollard, R.; Fouillot, J.P. “Human Vigilance in Railway and Long-haul Flight Operation. Ergonomics, Vol. 36, no. 9, 1993, pp. 1019-1033.
3. Cabon, P.; Mollard, R.; Coblentz, A.; Fouillot, J.P.; Speyer, J.J. “Recommandations Pour le Maintien du Niveau d'Eveil et la Gestion du Sommeil des Pilotes d'Avions Long-courriers.” Médecine Aéronautique et Spatiale, XXXIV, no. 134, 1995. pp. 119-128.
4. Cabon, P.; Mollard, R.; Bougrine, S.; Coblentz, A.; Speyer, J.J. “Coping With Long Range Flying. Recommendations for Crew Rest and Alertness.” Airbus Industrie, Blagnac (ed). November 1995.
5. Mollard, R.; Coblentz, A.; Cabon, P.; Bougrine, S. Vols Long-courriers. Sommeil et Vigilance des Equipages. Guide de Recommandations. Volume I: Fiches de Recommandations. Volume II: Synthèse des Connaissances de Base. French Direction Générale de l’Aviation Civile, Paris: October 1995.

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• Fatigue
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