The Pentagon signed a contract with Boeing on Thursday to supply Israel with four KC-46 refueling planes that are needed for potential Israeli strikes on Iran, although the aircraft won’t be delivered until at least 2025.

The deal is worth $927 million, and Israel is purchasing the planes from Boeing with money from the $3.8 billion in military aid it receives from the US each year. Of that amount, Israel receives $3.3 billion in Foreign Military Financing, a State Department program that gives foreign governments money to purchase US-made military equipment.

Israel has the option to order four more KC-46s in the future. The deal has been in the works for a long time, and Israel has previously asked the US if it could accelerate the delivery of the planes, but the US has denied the request. The US military would need to give up its spot in line to receive KC-46s in order for Israel to receive the planes earlier.