One practical way you could attempt to do this would be to massively tax airline tickets, ideally by distance flown, and then allow people to claim 4 untaxed tickets.
You could also maybe allow people to sell their tickets if they never intend to use them, which would create a new financial incentive for people to never get on a plane.
You could also maybe allow people to sell their tickets if they never intend to use them, which would create a new financial incentive for people to never get on a plane.