"reject just one flight plan, and allow the rest to proceed."
rejecting a plan wouldn't necessarily mean it doesn't exist/take off anymore, so that doesn't sound sensible
rejecting a plan wouldn't necessarily mean it doesn't exist/take off anymore, so that doesn't sound sensible
Or, if it's a "Bob owns a Cessna, and took off anyway" situation - well, Bob's license to fly a private airplane will probably be taken away. Maybe his Cessna, too. And (post-9/11) Bob could be spending some time in uncomfy little rooms with bars on the windows.
How?