WASHINGTON — The Pentagon made a $3.7 billion advance payment to Lockheed Martin late Friday for the 11th batch of F-35 aircraft.

The Pentagon and Lockheed still have not reached a final agreement on the 11th lot of F-35 aircraft, which is slated to cover 141 aircraft for the U.S. services and military partners. Although the Defense Department is confident it can hammer out a deal by the end of the year, it regularly uses a mechanism called a “undefinitized contract action,” or UCA, to dole out funding to Lockheed so that it can pay its suppliers and buy the materials it needs to meet the planned delivery schedule.

Friday’s award comes on the heels of a $5.6 billion UCA issued July 7, which obligated $4.5 billion for 91 F-35s produced for the U.S. Air Force, Navy and Marine Corps.

The July 28 award, which immediately obligated $2.2 billion, will allow Lockheed to continue work on 50 aircraft meant for international partners or Foreign Military Sales customers, including one F-35B aircraft for the United Kingdom; one F-35A aircraft for Italy; eight F-35As for Australia; eight F-35As for the Netherlands; four F-35As for Turkey; six F-35As for Norway; and 22 F-35As for unnamed FMS customers.

It also covers “scope for mission equipment and chase maintenance activity for the above mentioned participants, as well as the U.S. services,” the F-35 Joint Program Office said in a statement.

“Final aircraft prices for each customer’s variant will be determined upon final negotiations targeted for the end of this calendar year,” the JPO continued. “We are confident that the final negotiated Lot 11 aircraft unit prices will be less than Lot 10,” in which a conventional takeoff and landing F-35A model cost $94.6 million.

Deliveries on Lot 11 will start in 2019 and run until 2020.

Correction: An earlier version of this article used the wrong term for the contract mechanism used to obligate funds to Lockheed. It is an undefinitized contract action.