I have been to a few air shows on French military airfields - organisation has been superb - park on nearby disused airfield or out of town shopping car parks (shops closed Sundays), military busses run free shuttle, entry either €5 or €10, food fairly cheap so a family day out does not cost a fortune, and the shuttle back to the car park is efficient and quick. Leaving the car park a doddle.
Duxford a fortnight ago was good too (at least I have Friends of Duxford Seniors pass so £16 entry was not too bad), but free shuttle from Cambridge station was quick in both directions even without bus lanes near Duxford itself.