Efforts to reduce federal regulation of the nation's airline industry were advanced strongly yesterday as a congressional committee endorsed a liberal concept of permitting carriers to start new routes.

By a surprising margin of 13 to 3, the Senate Commerce Committee approved the centerpiece of a Carter administration-backed bill aimed at airline deregulation.

The so-called "automatic entry" provision would permit an airline to start one new route a year for the initial two years after passage and two routes a year for the next three years all without prior Civil Aeronautics Board approval.

Currently, the CAB must decide if an airline may serve a particular market. Under the amendment proposed yesterday by Sens. Howard Cannon (D-Nev.) and John Danforth (R.-Mo.), and accepted by their colleagues, gradual expansion into new markets would be permitted for a transitional period of five years.

Each airline would be allowed to designate some current routes as protected from new competition during the five-year transition. After that, total free entry into new markets could take place.

The Cannon-Danforth compromise ended weeks of deadlock in the committee on entry into new markets. Sen. Daniel K. Inouye D-Hawaii) tried to kill the section altogether and he was supported by labor unions.

Secretary of Transportation Brock Adams last night hailed the committee action on what he said was a "crucial element" of the airline bill. Hevowed to work for "early passage" of the legislation, once it leaves committee.

The Senate committee still must complete action on several provisions of the bill, which is expected to be approved and reported to the full Senate in the next few weeks.

Although many industry experts expect the Senate to pass the legislation, it is considered doubtful that a vote will take place before the planned congressional adjournment in mid-October.

The House Public Works and Transportation Subcommittee on Aviation plans hearings on similar legislation early in October, but no final House action is expected this year.

White House officals have said they expect congressional approval early in the new year. They say they expect the measure to be the first, significant Carter-backed step at reduction needless federal economic regulation, if finally enacted.

In related developments yesterday:

CAB chairman Alfred Kahn told a House subcommittee that the U.S. should seek more airline competition and less government restrictions in upcoming talks with Japan and other nations. U.S. - Japanese talks resume Oct.

Trans World Airlines said it would seek CAB approval for reduced advance purchase excursion fares (APEX) from all U.S. to all European cities. Fare cuts of up to $60 from current excursion rates would take effect Nov. 1, if approved.

The charter airlines industry asked the CAB to condition any approval of new APEX fares and so-called "budget" fares between the U.S. and London upon approval by Britain of more liberal charter rules suggested by President Carter. Charter officials also questioned Carter's authority to overrule the CAB's earlier opposition to some lower North Atlantic fares.

Britain's Civil Aviation Authority removed a restriction that had limited Laker Airways' flights to one per day in each direction across the Atlantic. Now Laker may schedule two flights a day, but the total number of available seats each daywill be reduced slightly.