AT LAST bill to begin the process of deregulating the airlines appears to be moving through Congress. The Senate Commerce Committee has rejected two proposals to weaken one of its most critical sections and may be ready to vote soon on the entire package. The committee ought to act as speedily as it can so that this major step toward ending unnecessary government regulation can reach the Senate floor before the session ends in October.

The two votes taken by the committee last week killed amendments that would have blocked any significant easing of the restrictions now placed on expansions of airline route systems. Presumably, the committee will now choose between permitting each airline to add each year, without government approval, one new route or two new totaling up to 3,000 miles. Both versions of this section of the bill are intended to open up competition in some airline markets. Neither is terribly daring, since each approaches this fundamental step in deregulating the airlines about as cautiously as possible.

Two other major aspects of the administration's bill have already received tentative approval by the committee. One of these would make it easier for airlines to drop service on routes that lose money. The other would give them considerable freedom to raise and lower fares without approval of the Civil Aeronautics Board.

Recent developments in the airline industry demonstrate why there is substantial support for these efforts to push the airlines into the world of competition. The sharp reduction in air fares between New York and London with the arrival of Laker Airlines in that markets if more competition were added. Similarly, the rash of lower prices on several domestic routes since the CAB began to approve discount fares so readily suggests that airlines will not be reluctant to use the power to change fares without approval, if Congress gives it to them. Of course, there is no guarantee that the new fares will remain low or that the lower prices will entice enough new passengers to make the flights profitable for the either the airlines (like Laker) that institute them or for the other airlines that decide they have to cut prices to meet the competition. But that is what a free market is all about.

It may be possible that the view of the CAB on regulation is changing so much that it will be able to bring substantially more competition to the airline industry in the long run. But it seems to us that a more orderly way of doing that, and certainly one that will have a more immediate effect, is contained in the bill now before the Senate committee.