More than half of the major Air Force bases in the United States operate at less than 50 percent of capacity, with no current plans to use their surplus space, according to an internal study suppressed by top Air Force officials.

The study says billions of dollars could be saved by closing up to 19 bases and moving some active-duty squadrons to Air Reserve or National Guard status. The report also predicts such moves would produce a more combat-ready Air Force with more efficiently distributed stockpiles of munitions and spare parts.The report, done at the behest of Congress and due nearly four months ago, was squelched by senior Air Force officials because its findings did not square with their objectives for the Air Force, according to Pentagon correspondence.

Instead of the report Congress had requested as part of last year's military budget bill, former Deputy Secretary of Defense William H. Taft IV on Feb. 16 sent a letter to the House and Senate Armed Services committees requesting more time to complete the study.

The study, prepared by a staff analyst under the assistant secretary of defense for program analysis and evaluation, suggests that military base closings and consolidations OK'd by Congress last week could be greatly expanded without sacrificing the capacity to house and service the Air Force fleet.

The main reason: Base facilities were planned for a 1950s Air Force that was far larger than it is now. U.S. military planners do not foresee any appreciable growth in the number of aircraft needed to protect American interests at home or abroad.

In the last 31/2 decades, the Air Force has reduced the number of its bombers, fighters, cargo planes and helicopters from 25,724 to about 9,200. Flying hours are down 63 percent.

Meanwhile, the cost in constant dollars of operating and maintaining this force has climbed from $21.9 billion in 1956 to $23.3 billion today, a 6 percent increase. Modern technology has made the planes and their service facilities more expensive.

Today, some bases are virtually empty:

- Whiteman Air Force Base, Mo., a giant Strategic Air Command facility, has no bombers or fixed-wing planes of any kind, yet it maintains a 12,400-foot-long runway big enough for B-52 bombers. Four HH-1H Huey helicopters are the only military aircraft assigned to the base.

- England AFB, La., with 72 close-air-support A-10 fighters, operates at one-quarter of its capacity, as does the pilot training base at Columbus, Miss.

Congress had asked for the report to find out if a dispersed airfield system that now houses F-16 fighters that fly twice the speed of sound is outdated and whether the Air Force could be modernized by moving active-duty squadrons to Reserve status.

The job of preparing the report for Congress was given to Franklin C. Spinney, a tactical fighter analyst and Air Force engineer. Spinney works at the Pentagon for Michael Leonard, principal deputy to David Chu, assistant secretary of defense for program analysis and evaluation. Chu's office, among other things, is responsible for the mix of active and Reserve forces.

Spinney, who refused to be interviewed for this story, completed the study by Dec. 22, according to a memo written by Leonard. Spinney used Defense Mapping Agency data on runways, parking areas and hangars, plus other information on aircraft base assignments, to reach his conclusions.

His findings prompted volleys of memos from Air Force brass:

A Dec. 11, 1988, staff summary report from Gen. Thomas E. Eggers, Air Force deputy director of plans, said the study "falls substantially short of current Air Force position."

A Jan. 6, 1989, handwritten memo from Gen. Larry D. Welch, the Air Force chief of staff, says, "Chief wants to meet with the person who wrote the study and his boss."

A Feb. 1 memo from James F. McGovern, acting secretary of the Air Force, said the study is "flawed in both fact and logic," and suggests a new report be developed "in a manner we consider least damaging to national security interests."

Air Force spokesman Capt. Sam Grizzle said the service would not comment on any unofficial report that has not been made public.

What Spinney found was that 36 of the 64 major Air Force bases were less than half-full, based on military planes and helicopters assigned to each base.