THE FEDERAL Aviation Adminstration has received more than 40,000 letters from the owners and operators of small airplanes who are outraged at the new rules it wants to adopt. "It's hard to know where public opinion really lies on this," the agency's adminstrator, Langhorne Bond, said recently. "We never hear from the 200 million airline passengers."

Well, no one can speak for all those passengers. But anyone who has flown and who knows lots of others who fly has an idea about what they would say if they did write. Most of them would favor the new rules the FAA has proposed-if they knew about them. Indeed, most would probably favor even tighter controls in the air and around major airports than have been proposed.

They would do so for a simple reason. When they step into an airliner, they place their lives in the hands of its crew, the air controllers and the other people who happen to be flying around in the wild, blue yonder. If Mr. Bond says their flights will be even safer than they now are after these new rules are adopted, they will be on his side.

Airline passengers, of course, do not have the problem of figuring out an air-safety program that protects them while preserving as much of the air space as possible for general aviation. In fact, many regard those private planes-everything from the single-engine Cessna to the four-engine corporate jet-as a threat to their personal well-being and would just as soon they were banished from the air.

The FAA can't-and shouldn't-do that because many of those airplanes serve useful purposes in addition to giving their pilots the joy of flying. But on those occasions when a small plane gets entangled with an airliner, millions of regular air travelers must wonder why the government tolerates the mixing up of small with big planes in the same air space. Never mind that the pilot of the small plane may have been faultless and the blame for the accident rest elsewhere. The argument is that if the small plane hadn't been there, the accident wouldn't have happened.

The balance Mr. Bond has to strike is a difficult one, and almost all the mail he has been getting has come down on one side. But from commercial airlines passengers' point of view, the new rules are a step in the right direction.