The Air Force has systematically breached the law and Defense Department regulations by providing top leadership with back-channel influence over promotion of generals, according to a bipartisan staff report made public yesterday by the Senate Armed Services Committee.

The disclosures revealed what amounted to a secret system-within-a-system of Air Force promotions, unknown to Congress or the secretary of defense for 30 years, according to senators and Pentagon officials. Thousands of officers were improperly crossed off eligibility lists, and top Air Force leaders routinely sought to sway supposedly independent selection boards.

The Air Force transgressions -- called a threat to "the integrity of the officer corps" by ranking committee members Sam Nunn (D-Ga.) and John W. Warner (R-Va.) -- raise questions about the legitimacy of the selections. Nunn said in an interview that he was unsure "what the legal ramifications are" but added the Air Force might "have to struggle with" legal challenges from officers passed over for promotion.

"There's nothing more sacred than promotion boards," said Sen. John Glenn (D-Ohio), chairman of the Armed Services manpower subcommittee. "They're behind locked doors, they're supposed to give their opinions without fear or favor and base {promotion} solely on what's in the record. This is so big that you can't believe something like this has been going on all this time."

Promotion boards in all military services are required by statute to operate under strict rules akin to those governing a jury in a civilian court of law. Each board consists of at least five officers, all of higher rank than the candidates they evaluate. The officers swear an oath to make their choices on merit "without prejudice or partiality" and solely on the basis of official military records. They are forbidden to communicate with anyone outside the board.

Only the Air Force was found to depart from those rules in a Defense Department review that was conducted by deputy personnel chief Robert S. Silberman and summarized in the Senate report. Among the unauthorized Air Force practices, likened by some Senate aides to jury-tampering, were:

Top generals of Air Force major commands conducted secret "pre-screenings" of all officers eligible for promotion to general, culling at least 85 percent of the officers from further consideration. There were no guidelines or standards governing their cuts. Another 5 percent of the eligible officers were cut in a second layer of pre-screening.

The selection boards, required by statute to consider all eligible officers, knew they never saw the records of about 90 percent of all colonels eligible for promotion to brigadier general.

The top generals routinely sent secret "priority lists" to each selection board specifying their preferences for promotion.

The presidents of selection boards routinely gave oral notice to the secretary and chief of staff of the Air Force of the board's choices for promotion to general before the lists were signed and became final.

The secretary, chief of staff and deputy chief of staff made direct and improper contact with selection boards. Those contacts appeared to result at least twice in a change of fate for officers about whom they spoke.

In the first case, the 1989 major general selection board "re-scored" its choices and promoted an officer who would not otherwise have been promoted after its president sought the advice of the then-chief of staff, Gen. Larry D. Welch. In the second case, the 1989 brigadier general selection board chose not to promote an officer after Lt. Gen. Thomas J. Hickey, who at the time was Air Force personnel chief, improperly told the board that the officer was a liar who lacked integrity.

Nunn said unanswered questions about "accountability" for the unauthorized practices would be addressed in the next session of Congress. In the meantime, he said, the committee has declined to confirm Hickey's nomination for retirement at three-star rank.

The Air Force system, little known outside the uppermost ranks, evolved in the early 1960s. Air Force Secretary Donald B. Rice, in an interview yesterday evening, said the system became improper after Congress passed the Defense Officer Personnel Management Act in 1981. But he portrayed the problems as purely procedural, saying all the promotions were still made on the basis of merit.

In 1987, after a scandal involving influence over a single promotion board by the secretary of the Navy and the commandant of the Marine Corps, Congress again strengthened the safeguards. Then-Defense Secretary Caspar W. Weinberger ordered each service to protect the independence of the selection boards.

"I simply wasn't aware that there were any questions about whether the Air Force was following those procedures until questions were raised by the Senate in the summer of 1990," Rice said. "Obviously, I inherited all that. Just as soon as I learned about it, we got it fixed."