The FAA gathers taxes per person, not per plane. So a commercial flight has every single passenger paying, while a private jet only pays for a few people. But the air traffic controllers aren’t handling individual people; They’re handling planes. So private jets fund the ATC a lot less than commercial flights, even though they have just as much need.

This video says Canada taxes planes based on weight rating and distance traveled. So larger planes that can carry heavier loads (more people) get taxed more, while smaller planes (private jets) get taxed less. But they’re proportionally paying the same in taxes, instead of the rich people paying less.