Unfortunately, the flight plan system has not quite kept up with the times. It should be possible to submit a change message to bring forward an EOBT.
That would get rid of the long winded cancelation, wait and re-file system we have currently which causes problems for everyone.
The +/- 15 minutes is correct but within 30 minutes of the filed EOBT, we deal with ATC who make any required changes to flight plans and slots........because we are in the aircraft not in the briefing room.
Thus, if the pax turns up 15 minutes early and we don't have a slot restriction, we tell ATC and it is up to them to make the required changes since it is now within 30 minues of the EOBT. Never had a problem yet!
Don't tell anyone that we got a direct last week that cut almost 15 minutes off our route time............shock horror, perhaps we should have refiled and got a slot so that we did not arrive early in some sector and cause an overload!
Regards,
DFC