Nathan Young wrote in message . ..
When filing en route, what do you use as the departure airport?

I don't use a departure airport. I use some convenient point
I will shortly cross or pass near. It can be a VOR, an NDB,
an intersection, degree-distance from a VOR, an airport. The
requirement is 1) to have something the computer will accept
2) to have something ATC can identify

I
always give the actual departure airport even though I left there some
time ago.

I would strongly recommend you DON'T do this. The reason is, if you
have passed into airspace controlled by another ATC facility, they
will not have your flightplan. The ATC computer will have sent
it to the ATC facility controlling the airspace around your departure
airport and there it will sit. In order to find your flightplan, ATC
will have to figure out where your departure airport is, who controls
that airspace, call 'em up, and say "depart that guy".

All problems you can avoid by simply filing from a point near your
actual geographic location at the time you file.

Cheers,
Sydney