Federal Aviation Administrator Langhorne M. Bond defended before Congress yesterday his controversial proposals for reducing the amount of airspace through which pilots can fly without submitting to air traffic control.

The proposals have generalted a bitter fight. The commercial airline industry and its passengers generally favor them, and the thousands of private plane and business aircraft interests generally oppose them.

Bond's proposals followed an FAA study of general traffic problems after a midair collision between a small private plane and a commerical airliner killed 144 people in San Diego last September.

In testimony before the House Public Works aviation subcommittee, Bond called his proposals "the logical evolution of our air traffic system." Rep. M. G. Snyder (R-Ky.), a subcommittee member and private pilot, said "I believe the FAA has grossly over-reacted" to the San Diego accident.

Snyder and other congressmen at the hearing reported their mail running heavily against Bond's recommendations. That did not surprise Bond; his is, too.

Bond would make three major changes in air traffic controls.

Under current regulations, all planes flying above 18,000 feet must file flight plans and submit to traffic control. Bond would lower that barrier to 10,000 feet east of the Mississippi River and over about one-third of California, and to 12,500 feet over the rest of the West.

Currently, pilots not qualified to fly on instruments cannot go above 12,500 feet. If the barrier were lowered to 10000 feet in some areas, fair-weather noninstrument pilots could enter the restricted area on clear days, but only under strict traffic control. Today, such pilots fly below 12,500 feet on a "see and avoid" basis, without reference to traffic control.

Under current regulations, 21 bigcity airports are surrounded by layers of tightly regulated airspace called Terminal Control Areas. Pilots flying into TCAs must submit to traffic control. Bond would add as many as 44 airports to the list of TCAs.

Taken as a whole, these restrictions are seen by the general aviation community as an enormous burden. Ten organizations -- including groups representing aircraft manufacturers, private pilots and business aircraft fleets -- recently joined to oppose the proposals as "unnecessary, unwarranted and drastic."

General aviation pilots would have to waste time filing unneeded flight plans and would be delayed in entering regulated airspace by overburdened controllers, they charge.

"We are genuinely convinced that FAA does not have the capability to provide the additional air traffic control services that would be required," J. Lynn Helms, vice chairman of the board of the General Aviation Manufacturers Association, testified yesterday.

"I can assure you... that none of our proposals will be implemented without my personal satisfaction that we do have adequate capacity," Bond said.

The charge most often leveled by the general aviation lobby is that none of the FAA's proposals would have prevented the San Diego accident. Bond said the same thing when he announced the proposals in December and he reiterated it yesterday.

"The true relevance of the San Diego accident," he said, is that it "caused us to focus on the general threat of midair collisions." The resulting proposals, he said, are subject to change before implementation, which could begin as early as this summer.