The Civil Aeronauties Board yesterday formally granted new coast-to-coast routes to four airlines, including two that have proposed one-way fares of $100 with no restrictions.

The board's decision could significantly alter the availability and the general price level of transcontinental air service.

Yesterday's action authorized unrestricted nonstop air service, effective March 13, by:

Capitol International Airways and World Airways, two formerly all-charter airlines proposing the low fares, between New Ork and Washington/Baltimore to the Los Angeles and San Francisco Metropolitan areas.

Pan American World Airways between New York and the Los Angeles and San Francisco areas. Pan Am's award is its first for unrestricted domestic authority.

American Airlines between Washington/Baltimore and San Francisco.

The board also authorized the big three incumbent airlines on the cross-country routes -- American, Trans-World Airlines and United Airlines -- to provide single-plane service between New York and Washington/Baltimore and Ontario, Calif. The board also moved to add even more potentrial service across the country: Five other airlines were told they would be allowed on the same routes if they could demonstrate in further proceedings that they are qualified to provide the service.In addition, the CAB said it would allow American, Capitol, Pan Am and World to expand the cities they could serve on their transcontinental flights unless they received comments from the public to convince them otherwise.

In its decision, the board said it thought granting awards to many airlines will produce the maximum potential for lower fares, innovative service, and increased efficiency as airlines make their own decisions about which markets to enter. Even if one or more of the airlines granted new authority does not start service immediately, the CAB said, the possibility that it may do so in the future without needing CAB permission will spur the carriers already operating to offer a variety of services and prices on those routes.

In another action, the CAB granted five airlines new routes to West Germany to take advantage of a recently signed agreement opening the way for more service there. Effective in week, the German awards went to:

Braniff International for flights to Frankfurt from Dallas-Ft. Worth, Detroit and Boston.

Capitol for flights from Chicago and New York/Newark nonstop to Frankfurt with a stop in Brussels if wanted.

Seaboard World Airlines for flights from New York to Cologne and Munich.

Trans International Airlines for service to Frankfurt from Los Angeles, Chicago and New York/Newark.

World for service to Frankfurt, Hamburg and Dusseldorf from Baltimore, Newark, Chicago, Detroit, Los Angeles and San Francisco/Oakland.