Braniff International this week asked the Civil Aeronautics Board for authority to fly between Dallas/Ft. Worth and London, one of the new routes to be opened between the United States and United Kingdom as a result of recently concluded negotiations.

If awarded the route, Braniff said it would designate a limited number of seats on each flight for a one-way fare of $250, a $40 per cent reduction from the current one-way regular economy fare between the two cities through connections.)

Billed as the "Texas Skytrain" fare, Braniff patterned it after Britain's Lker Airways' recently approved proposal to fly travelers on his "Skytrain" between New York and London for a one-way fare of $135. Like the Laker service, Braniff says it would offer the lower fare without reservations to travelers on a first-come, first-served basis six hours before flight time.

Under the terms of the new U.S.-U.K air agreement, airlines of both countries get air rights from four new U.S. cities to London. In the first three years of the agreement, U.S. airlines will be authorized to serve Atlanta and Dallas/Ft. Worth nonstop to London - one U.S. airline to a route - while a British carrier will get a Houston-London route. After the first three years, a U.S. carrier can get a Houston-London route, and a British carrier can serve the Atlanta and Dallas routes. In addition, another U.S. city may then be selected by the U.S. fr new nonstop authority to London.

The CAB has not yet decided how to proceed in fulfilling the terms of the new agreement. In a massive case completed by the board a year ago and sent to President Ford for a decision, the CAB recommended awarding a nonstop Dallas-London route to Pan American World Airways and a Dallas-London route to Delta Air Lines (with an intermediate stop in Atlanta). The case was sent back to the board pending the outcome of the recent negotiations.

Pan Am president William T. Seawell said earlier this week Pan Am still wants the route and would be ready to start service immediately if it got the CAB's okay.