How far in advance can you file a flight plan through Sky Demon?

For a VFR flightplan you will find this limited more by the staff at the receiving end, who are often dealing with a piece of paper that comes out of a printer. This piece of paper might end up in the bin if filed too far in advance. There is not much you can do about that. Normally filing 24 hours in advance works well in terms of both machine and human factors.

Used the flight plan functionality for the first time recently on a trepidatious flight over the oggin complete with jackets and raft. Quite marvellous. 50p per plan is good value for a great service. Very easy to use and it seemed to go through the system effortlessly. Well done.