I think the AIM (see 5-1-11) says that flight plans will stay in the ATC
computer 1 hour after departure. Also, AIM paragraph 5-1-7 says that: "
Pilots should file IFR flight plans at least 30 minutes prior to estimated
time of departure to preclude possible delay in receiving a departure
clearance from ATC.".

There's a lot of good information in that "little" book.

-Ali

"PaulH" wrote in message
om...
If I file an IFR flight plan 2 hours in advance from departure from a
towered airport and then leave really early or really late:
1. Is the FP normally available to my local tower about half an hour
after filing?
2. How long does it remain in the "system" if I get delayed?