Ten more hangars and office buildings could be built at Allegheny County Airport in West Mifflin over the next 20 years under a proposed master plan unveiled yesterday.

The Allegheny County Airport Authority is proposing to demolish 25 of 30 existing hangars at the site and build 35 new ones. They would be the first new hangars built at the airport in two decades, said JoAnn Jenny, authority spokeswoman.

It also is proposing to use land near a crosswinds runway that was closed in 2004 to build new office space, more hangars and an area for more corporate jets. The runway was converted to a taxiway, freeing up land for development.

"We'll be able to increase the number of tenants and development on the airport. That's something that hasn't been done for decades out there," Ms. Jenny said.

Under the new plan, most small private planes would be located in the lower western part of the airport. Corporate jets would be housed in the upper western section, along with the new office area.

The airport authority also is proposing to consolidate maintenance operations into a single building. It also is considering a common de-icing area for airplanes.

It will continue to lease out office space in the terminal building.

Authority Executive Director Kent George said in a statement the plans will "advance our mission of providing the region with the best facilities for general aviation, aeronautic education, aviation maintenance, and air medical transportation."

Ms. Jenny said the authority also is doing a financial evaluation as part of the master plan to determine how to make the Allegheny County Airport self-sustaining. Airlines operating out of Pittsburgh International Airport now contribute 10 percent a year, or about $260,000, toward that airport's budget.

The master plan, required by the Federal Aviation Administration, was discussed yesterday at a public meeting at the county airport. It still must be approved by the FAA.