FORT WORTH, Texas (AP) — Dallas-Fort Worth International Airport needs up to $10 billion in improvements to runways, taxiways and other parts of the airfield, its chief executive says.

"We have four runways that are 40 years old. We have roadways and bridges that are 40 years old," airport CEO Sean Donohue said in an interview with the Fort Worth Star-Telegram (http://bit.ly/2nqubAA ). "When you look at our airfield needs, that's several billion right there."

Donohue recently testified before a congressional committee about necessary improvements for the airport, which opened in 1974 and now uses seven runways.

The airfield is safe by government standards, but officials say the concrete and pavement of its runways and taxiways are reaching the end of their expected lifespan. Earlier this year, airport staff began testing airfield pavement to determine how many layers of runway will need to be rebuilt.

Fort Worth Mayor Betsy Price said the airport board hasn't yet been advised on what should be done first. Price says she supports funding for needed improvements.

"You don't want infrastructure that's crumbling and not going to be up to the quality you expect from this airport," said Price.

The airport is the world's third in operations and 10th busiest in terms of passengers, according to its website.

Airport officials support a bill, recently introduced in Congress, that would increase the maximum passenger facility charge that airports can add to airline tickets to fund capital projects. The fee has been capped at $4.50 per flight since 2000.

The airport has about $6 billion in debt from bonds sold to construct Terminal D, a new rental car center and to renovate Terminals A, B and E.