PITTSBURGH — The Allegheny County Airport Authority is expected to approve a $500 million deal with Consol Energy for rights to drill for natural gas and oil at Pittsburgh International Airport.

County Executive Rich Fitzgerald outlined the deal at a public hearing Thursday night. The authority board was expected to vote on it today.

Consol in December initially bid $20.8 million for drilling rights, which will include ongoing 18 percent royalties. Since then, Fitzgerald says the energy firm has agreed to increase its initial payment to $50 million and the royalties are expected to bring in $450 million more over the next 20 years.

Airport officials want to use at least some of the revenue to lower gate fees in hopes of attracting more airlines and flights to the airport about 10 miles west of the city.