It seems that you don't actually operate any flights, but are a travel agency that books the flights and services. That said... A couple thoughts.

It seems to me that most reward programs give the user something like 10% back(whether this is a sandwich card or a frequent flyer program). What does your customer base look like? How many are flying 10+ private jet roundtrips in a year or two? Those customers might be wooed by the offer of a free flight.

On the other hand if a lot of your customers fly by private jet once or twice a year I would try and focus on getting them to fly _once_ more a year. Some in flight amenity would probably be best here.

The last group are those that fly once - how do you get them to fly again?

Depending on what the market looks like, then you need rewards designed to meet that.

Also, be careful that you offer awards you can actually make money providing. Airlines provide class upgrades because it doesn't actually cost them very much to give you the upgrade (except in the possible sale of the seat). Same with award tickets. On the other hand, is your mark up so high that you can make money providing a "heavy" jet for the price of a "mid size" jet?

Also, the leisure issue is important. Most FF programs started and often focus on remaining a way to get flyers to choose a particular airline when someone else is paying. If these are people paying for their own flights, I might focus mostly on every flight value and amenities. And if you do a FF program, make it very simple low cost reward system (e.g. southwest).