Obviously you're referring to the present Luton Airport rather than the 'original' one at Barton in the Clay, where the Luton Minor and Major were developed.
Anyway my first visit was for a flight in the Chrisair DH Dragon (not Rapide) G-ADDI in about 1964. It was arranged by Air Britain (Chorleywood Branch - yes it actually existed!)and the pilot was Claire Roberts, wife of the owner Chis Roberts. It signifed several 'firsts' for me: first flight in a civil aircraft (but as a seasoned ATC cadet I'd flown in several miltary types), first in a biplane, and first with a 'lady' pilot.