If doing a Fly-in (Vs the Fun-Fly addressed in my earlier post):
Something to encourage more people to put planes in the air may be helpful.
1) a prize for most flights of the day.
2) A "Poker Fly" where you really need to fly 5 times to make a hand at all
and more gives cards to discard
(rules vary.. make em discard one before drawing thier 6th {no holding more than 5}... or hold all and choose at the end)
There's other encouragements to get the participants to keep planes in the air....