The Navy announced yesterday that two admirals and a captain have been fired for mismanaging the service's top priority aircraft program, the A-12 "stealth" bomber.

The extraordinary action by Navy Secretary H. Lawrence Garrett III came as the Pentagon released a highly critical internal report that documents "errors of judgment and failures of supervision" in the government's effort to manage a program that is now at least $1.3 billion over budget and 18 months behind schedule.

The carrier-based A-12 Avenger jet is scheduled to begin joining the fleet in the mid-1990s as a replacement for the A-6 attack bomber, now nearly three decades old and deployed in substantial numbers in the Persian Gulf. Each A-12 may cost $100 million, a Pentagon source said last night, a price tag likely to fuel the debate over whether the Navy can afford to outfit its 14 aircraft carriers with a new generation of airplanes.

Carriers typically carry 75 to 85 aircraft designed for different missions, such as hunting submarines or protecting the fleet against enemy aircraft. Attack bombers, such as the A-12 and A-6, are used to destroy ground targets or enemy ships. Like the Air Force's B-2 stealth bomber and F-117 stealth fighter, the A-12 is supposed to incorporate sophisticated "low observable" features that make detection difficult for enemy radar.

The internal Navy report released yesterday criticized the "culture" of Defense Department acquisitions in which obtaining funds and sustaining a program become more important than identifying and fixing problems. In the A-12 program, excessively optimistic cost and schedule estimates by the contracting team of General Dynamics Corp. and McDonnell Douglas Corp. were not challenged by Navy supervisors, the report added. Top Pentagon officials, including Defense Secretary Richard B. Cheney, were allowed to believe that the program was "on schedule, on cost and on track," according to the report, when in fact it was late, well above cost and performing poorly.

Vice Adm. Richard C. Gentz, commander of the Naval Air Systems Command, is being forced to retire by Feb. 1. Rear Adm. John F. Calvert, the program executive officer for tactical aircraft, and Capt. Lawrence G. Elberfeld, the program manager, have been removed from the program and formally censured, according to Navy officials.

A companion report by the Pentagon inspector general noted that General Dynamics required government inspectors last winter to relinquish their notes on the basis of "purported security considerations." One set of notes was lost. The inspector general questioned "any procedure by which a contractor obtains access to, and control over, the work product of government personnel engaged in oversight duties." General Dynamics declined to comment last night; a McDonnell Douglas official said his company is reviewing the critical reports.

Last April, Cheney announced after a review of the program that A-12 development would continue, although the Navy's original request for 854 aircraft was trimmed to 620. The estimated cost of the program at that time, according to a Pentagon source, was $52 billion.

But several weeks later, McDonnell Douglas and General Dynamics informed the Navy that the plane was behind schedule, unable to perform as required and so far over the supposedly fixed-price contract that the contractors "could not absorb" the costs. That disclosure shocked the Navy and Defense Department, triggering the six-month investigation that culminated in yesterday's announcement.

In a letter to Cheney, Garrett acknowledged his "responsibility and accountability to you" and disclosed the disciplinary action against the A-12's top three Navy managers.

A spokesman for the Naval Air Systems Command, which has 48,000 employees worldwide, said the three disciplined officers had no comment on Garrett's action. Gentz, a pilot who has been in the Navy 33 years, issued a two-paragraph statement that made no reference to the disciplinary action.

The fate of the A-12 will be considered Friday by the Defense Acquisition Board, a high-level Pentagon panel that oversees major projects. A Pentagon source said he does not expect the project to be scrapped, but believes that full-scale production may be delayed "until after the plane and technology prove themselves. If that happens, the plane will cost more." The Navy also has considered other bomber options, such as developing a bomber version of the F/A-18 Hornet or F-14 Tomcat fighters, the source added. Rep. Andy Ireland (R-Fla.) yesterday called for congressional hearings into the matter.

The inspector general also sharply criticized John A. Betti, undersecretary of defense for acquisition, for relying too much on the contractors' assurances and for dismissing warnings from lower-level Pentagon officials. A Defense Department spokesman said Betti would have no comment. Cheney, according to a statement issued by his office yesterday, has requested further recommendations for corrective action when he returns from Europe later this week.

Unless fundamental changes are made in the acquisition "culture," the Navy report warned, "the failures evidenced in this report can be anticipated to occur again in the same or similar form."

Staff writer Martha Hamilton and staff researcher Lucy Shackelford contributed to this report.