The White House formed a committee of senior officials to help decide how the new Air Force One should be configured after Michael K. Deaver suggested the White House should play a greater role in selecting the new presidential aircraft, a former administration aide testified yesterday.

The testimony by Dennis Thomas, a former deputy to White House chief of staff Donald T. Regan, was one of the few instances in which a suggestion by Deaver, who left the White House to become a lobbyist, apparently led to immediate action by his former associates.

Deaver, a longtime confidant to President Reagan and his wife Nancy, is on trial in U.S. District Court on charges of lying to a congressional subcommittee and a federal grand jury about his contacts as a lobbyist with senior Reagan administration officials.

Yesterday, the 16th day of testimony in the case, brought differing assessments of Deaver's work on behalf of Boeing Co., which was bidding to sell the Air Force two new presidential jets.

Edward M. Collier, a retired Air Force officer and a representative for Boeing in Washington, told the jury that he was discouraged after Deaver told company representatives that Boeing's plan to put enough seats to accommodate a presidential party of 84 on the 747 jet would not work. "He said there were too many seats on the plane and it would be a scheduler's nightmare," Collier said.

Collier also said he told William Sittman, a Deaver associate, that he believed Sittman's suggestion for a White House representative to sit on the Air Force selection panels judging competing models was a good idea, although he privately thought the idea outrageous. "I didn't in my wildest dreams think it was possible" because of the amount of time serving on the panels would take, Collier said.

Thomas, who assumed many of Deaver's responsibilities when he became an aide to Regan, gave his account of what Deaver did in return for the $250,000-a-year lobbying contract he had with Boeing.

Thomas offered a vague recollection of the contact with Deaver, saying he could not recall if they spoke by telephone or in person.

According to Thomas, Deaver asked him if he were involved "in the question of a new Air Force One, ensuring institutionally the White House had input as to how the plane was configured." At the time of the suggestion, in the fall of 1985, Thomas said, he knew Regan had approved ordering a new plane, but had little knowledge of how the selection process was going.

Thomas said he decided Deaver's idea "seemed to be appropriate" and, with Regan's approval, convened a committee of White House staffers to give advice to the Air Force on how the new plane was configured. It was a process he compared to advising "an architect . . . on house plans."

The committee met about five or six times with the approval of White House lawyers. The lawyers had issued instructions that anyone attempting to contact them about purchase of the new plane be referred to the Air Force contracting office "in order to avoid even the appearance of any improper interference."

McDonnell Douglas Corp. then was offering its DC10 jet as an alternative to the 747. When the Air Force suddenly changed takeoff requirements for the plane, Collier said some senior Boeing officials were convinced that some military officials were trying to steer the contract to McDonnell Douglas.

Boeing, which ultimately won the contract, had hired Deaver shortly after he left the White House over Lyn Nofziger, another former Reagan aide. Collier said he favored Deaver for the job because "Mr. Deaver was closer to the personal tastes and preferences of the president."

Defense lawyers said it was a legitimate concern in light of the $1.5 million in remodeling Boeing had to do during the Nixon administration after First Lady Pat Nixon viewed a new Boeing 707 being planned for the presidential fleet and made numerous suggestions that led to changes in the design of the interior.