Actually, simpler than that.
This gets lots of press that a flying random air cadet doesn't. That press can be used to raise money from other sources - allowing more children the opportunities to fly anything at all.
If the calculation was as simple as:
1x cadet for 1 flight in a jet.
Or
10x cadets for 1 flight in a Grob
Then it's a no-brainer that Carol gets the jet gig, so 10 cadets get the Grob gig...