On the eve of Senate Commerce Committet consideration of major legislation to reduce federal regulation of the airline industry, President Carter yesterday stepped up his personal support for its enactment.

"There is a tremendous potential market among Americans for airline service use that hasn't yet been tapped," the President told a packed briefing of officials of the airline and related industries and congressional staff.

He said the pending legislation "substantially overcomes" concerns raised about earlier proposals and would protect communities from a loss of air service. At the same time, the legislation would spawn lower fares, greater flexibility for the airlines to accommodate to changing market conditions, and new entry into the airline business, the President added.

"We want to have an opportunity for strengthening the free enterprise system in our country, to make sure that competition exists in a fair and equitable way, and to be sure that we have some protection for small communities that now receive commercial airline service," President Carter said.

Cognizant of opposition to the measure from the majority of the airlines and their unions -- many of whose leaders were in the room -- he said. "There is always a fear of change, and I know that when there is a privilege that is now extant, the chances of losing that privileged position is one that causes legitimate concern." But he repeated his view that reducing regulation might well reinvigorate the airline industry as well as provide better service to travelers and communities.

The President was flanked at the briefing by Transportation Secretary Brock Adams: Attorney General Griffin B. Bell; acting assistant attorney general for antitrust; John H. Shenefield, Senate Aviation Subcommittee Chairman Howard W. Cannon (D-Nev.); Senate Antitrust and Monopoly Subcommittee Chairman Edward M. Kennedy (D-Mass.); Reps. Norman Y. Mineta (D-Calif.) and Elliott H. Levitas (D-Ga.), both members of the House Aviation Subcommittee: and Civil Aeronatucs Board chairman Committee would begin consideration Alfred E. Kahn.

Cannon said the Senate Commerce today of the measure, which was put together over the last few weeks at the direction of Cannon. Kennedy and two key Republican committee members, Sens. James B. Pearson (R-Kansas) and Ted Stevens (R-Alaska).

The proposal places a greater emphasis on transition and moderation as the industry is moved from strict regulation to an enviroment in which competitive market forces play a greater role in determining what fares and services the carriers make available to the public.

"Let me say right off that there is no one involved in this effort who has any desire to injure or to destroy the air transportation industry. . ." Cannon told the assemblage. "We want to do things we can do to promote that industry and to promote the benefits to the flying public. . ." He said the sponsors of the bill were not wedded to any particular point in it and were willing to listen to proposed changes. "On the other hand, I think we are firmly committed to trying to get some regulatory reform truly under way," he added.

Although the Senate appears to be moving on airline legislation, little of substance has happened this session in the House. But yesterday both Mineta and Levitas pledged to introduce the bill the Senate produces as a mechanism for consideration in the House.

CAB chairman Kahn issued a general, but passionate, endorsement for change. "I feel very strongly that I need a set of new instructions from Congress," he said. "I'm pledged to enforce a law that was passed 40 years and. . . is clearly promotional and protectionist in its orientation.

DOT secretary Adams, who on occasion has appeared to be a reluctant support, appeared yesterday to be a wholeahearted supporter. "We are now very satisfied with this bill," he said. "We want to see it move."