I understand this is a partisan fight issue, our policy of most rationality vs. their utter barbarism type of discussion. But please:
Air traffic safety is an important service. Why would that need funding from the government, if so many customers need and purchase that service?
Every flight passenger is using this service to get from A to B safely. Every flight passenger is buying a ticket that includes all sorts of fees and taxes, including airport security. (we disregard a debate about the TSA for now).
Why don't all airlines PAY for the FAA service proportional to the number of flights they perform? Why would "the taxpayer" have to fund and subsidize "the airline passenger"? Why would the state go into more debt to pay for something that is a commercial service to a select few people, many of which are tourists or foreigners who don't even pay US taxes in any substantial amount.
Use a service -> pay for that service.
If John is purchasing a flight ticket and boards an airplane, his ticket must include all the costs required to do that safely. John cannot expect some random Steven and Michael to pay for that with their taxes. It's John's flight. John pays for John's safety. Steven and Michael aren't traveling right now and so they don't pay anything. If they were to travel later, they, too, will pay for safety of THEIR flights, respectively.
Everything else is immoral. I don't understand why this is an issue at all.