If there is a delay in the first flight of a crewmember’s FDP, the crewmember could go over their max FDP duty limit before their FDP is complete.  However, there is a legal “cheat” that may allow the crewmember to complete the FDP, without reaching their max limit. When you become aware of the delay, the crewmember can be placed on reserve for the time between when the crewmember was originally scheduled to report and the new adjusted report time.  This adds 4 hours to the MAX on duty and his report time is still adjusted, giving the company a longer window to operate the FDP without the crewmember reaching their max limits.

For example, Crewmember had a report time of 1400.  However, the FDP was delayed by 2 hours.  Company can place the crewmember on reserve for the 2-hour delay, giving the crewmember a buffer and the company a longer window before the crewmember meets the max duty limit.