[jleahy]

Well they can reject the bad flight plan and the plane will not be allowed to follow it.

[nirse]

Do you know what the consequences of that would be?

[jleahy]

Yes, it happens to people every day for all kinds of boring reasons. Normally because they made a mistake in their flight plan.

Remember anyone flying IFR needs a flight plan, lots of private pilots etc. Plenty of people make mistakes.