Near completion of its work on a measure to reduce regulation of the airline industry, the House Aviation, Subcommittee yesterday put back into the bill a provision designed to give the airlines some freedom to fly new routes without getting prior government approval.

Two weeks ago at the subcommittee's first markup session on the bill, a provision authorizing the Civil Aeronautics Board to set up such a program was deleted.

The amendment adopted yesterday by a vote of 14 to 9 would give the airlines the ability to enter three new routes over the next four years without having to submit to CAB hearings.

Sponsored by Rep. Allen E. Ertel (D-Pa.), the provision would allow existing federally regulated airlines and major intrastate carriers to start one new nonstop route during the second year after the bill passes. In the fourth year, the carriers could start nonstop service on two more routes.

The carriers would apply for the new routes, but the CAB would have to approve them unless the new route would substantially impair the national air transportation system or cause a substantial reduction in service to small an medium-sized communities.

"We have to start somewhere . . . if we are going to move to a less regulated climate," Ertel said in defending his provision. He called it a "moderate" provision that would result in a gradual process of opening up the industry to greater competition.

The administration and the CAB support inclusion of some form of automatic market entryas a way of forcing airlines to begin making their own market decisions. They also argue that a realistic threat of competition will keep existing carriers from unwarranted fare increases.

Rep. Elliot H. Levitas (D-Ga.), who sponsored the move to take the original provision out of the bill, argued yesterday that the rest of the bill - a pro-competitive policy statement, expedited board precedures and new authority to apply for routes carriers aren't sing - would move the industry to a more competitive environment.

The subcommittee also adopted a very broad labor protective provision. More generous than the pending Senate bill, the amendment would not allow any airline to take advantage of any of the bill's provisions unless the Labor Secretary certifies each time that the interests of the airlines's employes who may be affected "have been adequately protected." The air line is responsible for applying protective arrangements, but will be reimbursed by the U.S. Treasury for whatever funds it takes.

Rep. Norman Y. Mineta (D-Calif.), who sponsored the labor protection provision, said it is necessary to protect employes who may be displaced by the act. Nearly everyone voted for it, even though some noted it authorizes "a blank check" that the American taxpayer would be picking up.

The subcommittee may well finish the markup of the bill today.