US Airways’ contention that bigger airlines are better for the public got unexpected support Wednesday from a senior official in the U.S. Department of Transportation testifying at a Senate hearing on airline mergers.

Since Sept. 11, the declining health of network carriers has created a growing need to subsidize air service to smaller communities, Andrew B. Steinberg, assistant secretary for aviation and transportation affairs, told the Senate Committee on Commerce, Science and Transportation — many of whose members represent largely rural states like Alaska, West Virginia and Minnesota.