The Port Authority of New York and New Jersey and the Bush administration are heading to court over a proposal to auction off takeoff and landing slots.

The Port Authority filed a motion with the U.S. Court of Appeals for the District of Columbia Circuit yesterday requesting to join an earlier suit that seeks to invalidate the federal Department of Transportation’s plan to auction flight slots at John F. Kennedy International, La Guardia, and Newark Liberty International airports.

The Port’s motion was prompted by the Department of Transportation’s threat to withhold $27 million in grants if the agency continued its resistance to the slot auction plan.

The Department of Transportation asked for a formal review to determine whether the Port Authority, which operates the airports, would violate federal regulations if it followed through with its previous proposal to punish airlines that participated in the auctions by barring access to gate space in terminals or parking positions on the airfield at the three airports.

“If the proposal by the Port Authority is in fact discouraging open access to the airports, the Port Authority may no longer be eligible for FAA grants, or payments under existing grants, until the matter is resolved,” the Department of Transportation said in a statement.

The Port Authority is joining the original plaintiff, the Air Transport Association — an umbrella organization representing the airlines — which filed the suit last month. The suit alleges that Congress never authorized the Federal Aviation Administration to auction slots.

The Port Authority says the proposed slot auctions would result in higher costs for airlines, increased ticket prices for passengers, and fewer flights to smaller destination cities.