A $5 million federal subsidy to Colgan Air Inc. is like a pat on the back to the company for maintaining service to airports in Owls Head, Trenton and Augusta, an aide to U.S. Sen. Olympia Snowe said Monday.

Colgan will receive $2.7 million this year and about $2.3 million next year under the Essential Air Service program of the U.S. Department of Transportation. In the last two-year budget, Colgan landed about $4.6 million under the program, said Dave Lackey, Snowe’s spokesman.

Snowe serves on the aviation subcommittee of the Senate Commerce Committee.

The subsidy acts as an incentive, Lackey said, to keep carriers like Colgan providing regular passenger service to small airports in rural areas like Maine. Colgan operates 19-seat aircraft providing 12 nonstop and 12 one-stop flights weekly between Maine and Boston.

The Hancock County-Bar Harbor Airport in Trenton serves nearby Mount Desert Island and Ellsworth; the Knox County Regional Airport in Owls Head serves nearby Rockland; and the Augusta State Airport serves the state’s capital area.

The Essential Air Service program was established in 1978 to protect rural communities from the effects of airline deregulation.

The amount of the subsidy is based on the numbers of passengers and flights, the cost of landings, and training of crew, Lackey said.

Colgan Air entered into a partnership with US Airways Express two years ago, which has boosted the number of passengers using the small airports. Traffic for the airports has nearly doubled over the past six years, from 29,800 passengers in 1994 to 57,671 for 2000.

Colgan also provides service between Boston and Rutland, Vt.

Colgan in based in Virginia.

Lackey said Snowe is still working on ways to improve regular commercial passenger service to airports in Bangor and Presque Isle.