Originally Posted by
tennisguru
Correct, any reroute must be legal without an extension at the time it is assigned. After that all the normal FDP limits and extensions apply.
Many times this is why you cannot be put back on your original delayed flight that you were rerouted out of. Once you have your reroute schedule any further change must be legal without the extension, even if it was on your schedule earlier in the day.
Legal but not reasonable. I've been rerouted into an extra leg that showed 10 minutes from block in from one leg to block out of the next in order for the extension to be "legal". Then when you somehow can't manage to make that tight turn and are "delayed" into your extension, it's on the pilot to call in fatigued or unfit for duty. The company's ethics can often be suspect.