NEXT TIME you're crammed into a middle seat on an airplane waiting for takeoff at a congested airport, you might notice a private airplane or two also waiting in line. The relatively few occupants of those planes will, of course, be a good deal more comfortable than you are and you might want to reflect that, as a taxpayer and commercial flier, you are helping to pay for their comfort.

Every form of transportation in this country -- even walking on sidewalks and roads -- benefits from government subsidies. But general aviation -- individuals and firms that own and operate airplanes for private and business use -- is especially favored. Most federal spending for airports and controllers is financed by taxes on commercial passenger tickets and aviation fuel. But taxes and fees paid by private plane owners cover less than one- fifth of their share of federal aviation expenditures. The rest comes from higher airline passenger fares and contributions from the federal Treasury.

And, of course, commercial airline passengers pay for private planes in another way -- in time lost waiting on runways and circling airports. Keeping general aviation out of major airports at peak times wouldn't eliminate congestion, but it would certainly help. The hyperactive general aviation lobby, eager to demonstrate its importance to U.S. aviation, points out that general aviation accounts for more takeoffs and landings than do the commercial carriers at 71 of the 100 busiest FAA-towered airports in the country. The lobby doesn't point out that, while absorbing the same controller and runway time as commercial flights, private flights carry only a tiny fraction of the passenger load and pay much lower landing fees.

A pure free-market approach to airport access would auction off all takeoff and landing slots to the highest bidder. This would probably drive general aviation out of big airports entirely, and would certainly keep it out of prime-time slots. That drastic a solution, however, wouldn't necessarily be in the public's best interest, either. As general aviation advocates and the smaller airlines will point out, many travelers would be seriously inconvenienced if small connecting flights couldn't land at major airports.

Still, as far as the traveling public is concerned, the current method combines the worst aspects of unfettered competition, inefficient government subsidization and private deal-making among major competitors. Improving the system will probably require adjustments in many things, but it must surely involve making sure either that private planes don't add to airport congestion, or that they pay the full cost of their contribution.