Slot delay, report time and the commander's discretion
A two-pilot crew flying a twin-jet on a domestic scheduled service reports at 05:10 local. The operator's approved scheme allows a maximum basic flight duty period of 13 h for two sectors and 12 h 30 min for three or more, with no extension other than commander's discretion. Three sectors are planned: off-blocks 06:00, 09:15 and 12:30, the last landing at 14:20. At 04:00, before the crew reported, the flow unit publishes a regulation giving slots of 08:40, 12:20 and 16:00; the last landing would then be 18:20. Nothing suggests further delay and the weather is fine. The first officer flew the same pattern on each of the previous four days and mentions he 'slept badly'. The dispatcher's note reads: 'Just a slot delay - the commander can sort it out on discretion.'
1. Compute the latest permissible landing time under the basic flight duty period and state whether the revised plan is lawful.
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The FDP begins at the report time, 05:10, not at off-blocks. With three sectors the basic maximum is 12 h 30 min, and the FDP ends at the last landing (engines off), not at the last take-off.
- 05:10 + 12:30 = 17:40 latest landing.
- Revised plan: last slot 16:00, sector time about 2 h 20 min, landing 18:20.
18:20 is 40 min beyond the basic limit. With no pre-agreed extension in the scheme, the plan as re-planned at 04:00 is not lawful under the basic rule; it can only be flown if a permitted extension mechanism is correctly invoked. Note also that the crew is on its fifth consecutive day of the same pattern, which is relevant to the fatigue assessment that must accompany any extension.
2. The dispatcher, the operator and the commander each have a role here. Which mechanism could have preserved legality, and what conditions attach to it?
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Because the regulation was published at 04:00 - 70 min before the crew reported - the delay was known in advance, so the correct mechanism is a re-planned (delayed) report time, not commander's discretion.
- Move the report to, say, 06:20: the 08:40 slot still allows a normal pre-flight. FDP then runs 06:20 to 18:50, and an 18:20 landing is comfortably legal and needs no discretion at all.
- Responsibility: the operator/dispatcher must plan the duty so it fits the scheme; the commander is the final authority on whether to accept the duty as presented, but must not use discretion to paper over a delay the operator could have planned for.
Commander's discretion is reserved for unforeseen circumstances arising after the FDP has begun. A slot published before report is foreseeable. Discretion is also bounded by the scheme (typically a stated maximum of one to two hours, once per duty period), must be justified by the circumstances, and must be recorded and reported; it cannot be used routinely or to protect a schedule.
3. Suppose the crew does report at 05:10 and the second slot then slips a further 90 min, after departure, because of a pop-up thunderstorm. The last landing would be 19:50. What is the commander's position and what must follow the flight?
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Now the delay is unforeseen and occurs after the FDP has started, so discretion is the right mechanism - but only within its limits. Basic FDP end is 17:40; 19:50 is 2 h 10 min beyond it, which exceeds a typical two-hour discretion cap. So the answer is not simply 'yes':
- Recompute against the actual scheme's discretion limit. If the limit is 2 h, the latest landing is 19:40 and 19:50 is still unlawful - the sector must be re-planned (a different aircraft/crew, dropping the last sector, or landing short).
- If the discretion limit is not exceeded, the commander may extend only if the crew's fatigue state is acceptable at that moment. Five consecutive days of the same pattern plus the FO's poor sleep is a negative factor; the commander should state the reasoning, not just the arithmetic.
After flight: record the discretion and its justification in the flight documentation, report it through the operator's fatigue-reporting system and to the authority as required by the scheme, and confirm that the minimum rest before the next duty is not reduced.