AD OPT, a Kronos Division FDT Final Rule Clarifying Questions May 4, 2012

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FDT Final Rule Clarifying Questions

Section 117.3 Definitions

Theater:

Theater means a geographical area where local time at the flightcrew member’s flight duty period 

departure point and arrival point differ by more than 60 degrees longitude.

1. Could you please confirm that the term “local time” in the definition is unintended? We believe 

that this is just a remnant from the former NPRM definition of theater. Will this be corrected?

2. Does the above definition actually refer to “duty period”, as opposed to flight duty period (FDP), 

where “duty period” extends from the beginning of sign-in (report) to end of sign-off (release)? 

Our reasoning is that a flight duty period does not include deadheads after the last operating 

flight. These deadheads can take crewmembers outside of a theater or bring crewmembers 

back into a theater before the end of a duty period (e.g., ORD-JFK followed by deadhead from 

JFK to LHR, or HNL-JFK followed by a deadhead from JFK to LAX). Accordingly, it seems to us 

that these deadheads must be taken into account when determining the crew’s acclimation 

state at the end of a duty period.

3. What station should be used as the reference point for determining the extent of a theater – the 

departure station of a duty period or the station where the flight crew were last acclimated? 

Our interpretation of the above definition is that flight crew members remain in a “theater” as 

long as the difference in longitudes between the first station and the last station in a duty period 

is less than or equal to 60 degrees. 

Moreover, the 60-degree geographical area can shift from one duty period to the next, instead 

of being anchored at a location where the flight crew members are either acclimated or trying 

to gain acclimation. This is because the extent of the theater is calculated as the difference 

between the “departure” and “arrival” stations of each duty period, rather than the difference 

between the “departure” station and the station where the flight crew members are acclimated 

(or attempting to gain acclimation).

For instance: 

 Crew members can depart from New York (JFK) on Day 1 acclimated to JFK and travel to 

Los Angeles (LAX) while maintaining their acclimation, since the difference in longitudes 

between the departure and arrival stations is less than 60 degrees. For this duty, the 

theater extends from JFK to LAX.

 On Day 2, the same crew can operate a flight from LAX to Honolulu (HNL) while 

remaining within a 60-degree geographical area that extends from LAX to HNL. The crew 
AD OPT, a Kronos Division FDT Final Rule Clarifying Questions May 4, 2012

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would not lose acclimation, since their net movement during the second duty remained 

within one theater – even though they are now more than 60 degrees away from their 

home base (JFK). The crew would enter the FDP table based on JFK local time on Day 2, 

since the crew never lost acclimation when travelling to LAX on Day 1. For this duty, the 

theater extends from LAX to HNL.

 Using the same logic, the crew could then continue on to Fiji (SUV) on Day 3 and still 

remain “acclimated”, since the longitude difference between the duty period departure 

point (HNL) and arrival point (SUV) is less than 60 degrees. For this third duty, the 

theater extends from HNL to SUV and the crew would still be acclimated to JFK. 

 In summary, as long as the crew’s net movement during a duty does not extend beyond 

the 60-degree-wide geographical area anchored at the point of departure, the crew 

could keep on moving in this fashion (theoretically, around the globe) without ever 

losing acclimation. Was this the original intent of the theater/acclimation definitions? 

Could you please clarify how the ruling works for this type of situation?

Another example:

 Crew members can depart from Los Angeles (LAX) on Day 1 acclimated to LAX and travel 

to Honolulu (HNL) while maintaining their acclimation, since the difference in longitudes 

between the departure and arrival stations is less than 60 degrees.

 On Day 2, the same crew operates a flight from Honolulu (HNL) to New York (JFK). 

According to the definition in the final ruling, the flight crew would lose acclimation 

upon arrival at JFK, since the difference in longitudes between the departure and arrival 

stations exceeds 60 degrees. However, the flight crew departed from HNL acclimated to 

LAX, which is less than 60 degrees longitude away from JFK. Should the flight crew 

members really lose acclimation to LAX in this situation?
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Acclimated:

Acclimated means a condition in which a flightcrew member has been in a theater for 72 hours or has 

been given at least 36 consecutive hours free from duty.

1. For the purpose of determining the maximum FDP limit in Table B, should the acclimation 

reference station ever change for acclimated crew operating within a theater?

a. Case 1: After 36 consecutive hours free from duty. For instance, consider LAX-based 

flight crew members who operate to JFK and then get a 36-hour layover at JFK. Our 

understanding of the final ruling is that LAX local time would apply to Table B for the 

next duty out of JFK, since flight crew members remained in the same theater when 

operating from LAX to JFK. In other words, the acclimation reference would not change.

Now, consider LAX-based flight crew members who operate to LHR and then get a 36-

hour layover at LHR. Our understanding of the final ruling is that LHR local time would 

apply to Table B for the next duty out of LHR, since flight crew members were given 

sufficient rest at LHR to acclimate to the new theater. While this change in acclimation 

reference from LAX to LHR does not seem unreasonable, we are wondering why 36 

hours rest would be sufficient for LAX-based crew to acclimate to London (LHR) local 

time, while LAX-based crew flying out of JFK after the same amount of rest would not be 

considered acclimated to JFK? 

b. Case 2: After 36 consecutive hours free from duty (successive “small” hops). If the 

theater interpretation allows flight crew to maintain acclimation by travelling in lessthan-60-degree hops, would the acclimation reference station for Table B not change 

even if the flight crew members were very far away from their home base? For 

instance, consider JFK-based crew who travel westward in successive less-than-60-

degree hops (i.e., JFK-LAX-HNL-SUV) and then get a 36-hour layover in Fiji (SUV).
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c. Case 3: After operating in the same theater for 72 hours. We would expect the answer 

to be “no” in this case, mainly because it would be very tricky to manage. However, if 

the theater interpretation allows flight crew to maintain acclimation by travelling in lessthan-60-degree hops (please refer to our Theater question above), the question begs to 

be answered. For instance, consider JFK-based crew who travel westward in successive 

less-than-60-degree hops around the globe. Would the reference station for Table B 

always be JFK, even if they find themselves in Asia and have been away from their home 

base for, say, one week?

2. When flight crew members lose acclimation, at what station do they regain acclimation?

a. Case 1: After 36 consecutive hours free from duty. According to the definition, flight 

crew members would regain acclimation at a station where an opportunity for 36 

consecutive hours rest has been provided. For instance, JFK-based flight crew who lost 

acclimation after a flight from JFK to CDG would regain acclimation at CDG following a 

rest at CDG of 36 consecutive hours or longer. But, what would happen if the crew did 

not get 36 consecutive hours of rest before operating to London (LHR) and the 36 hours 

rest was given at LHR – would the crew members be acclimated to CDG or to LHR? 

b. Case 2: Flight crew enter a new theater and continuously work in that same theatre for 

72 hours. Consider a situation where a flight crew based in JFK operates a flight to LHR 

(new theater) and then continues to operate flights in Western Europe (say, France, 

Spain, and Italy) over the following 72 hours.

i. At which specific station does the flight crew regain acclimation, for the purpose 

of entering FDP Table B? Is it the first station where the flight crew lands upon 

entering the new theater (in this case, LHR)? Is it the first station where the 

flight crew members have a rest around the 72-hour mark?
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ii. What happens if the flight crew moves successively eastward in less-than-60-

degree hops per duty period during the 72 hours, after having lost acclimation 

at LHR? Suppose, for instance, that the flight crew performs the following 

sequence of duties: JFK-LHR- PRG-MOW-ALA

At which specific station does the flight crew regain acclimation, if 36 

consecutive hours of rest are never achieved? Please note that the difference in 

longitude between London (LHR) and Almaty (ALA) is approximately 76 degrees.

Thank you in advance for your assistance with our questions.

Philip Ifrah, M. Eng., MBA

Product Manager, AD-OPT Division

Kronos

t: +1 514 764 8295

f: +1 514 345 0422

philip.ifrah@kronos.com

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