The Royal Australian Air Force (RAAF) formally bought its first four P-8A Poseidon maritime surveillance aircraft in a $1.49-billion contract with Boeing that also includes the U.S. Navy’s next nine aircraft, Boeing announced today.

Australia’s participation in the program goes back to 2009, and though it has recently procured a complete training system and signed a contract for long-lead materials, it had not formally signed a contract for its aircraft.

The RAAF announced in February 2014 it intends to buy eight P-8As to replace its AP-3C Orions, and could buy as many as 12 pending the outcome of a Defence White Paper review. It said the first aircraft would deliver in 2017 and the full 8-plane fleet would be operational by 2021.

The contract announced today keeps ahead of that schedule, with Boeing saying that “production of the first Australian P-8A will begin later this year, with delivery to the RAAF scheduled for 2016.”

“By working together since the early stages of P-8A development, the U.S. and Australia have created one airplane configuration that serves the needs of both countries,” Capt. Scott Dillon, U.S. Navy P-8 program manager, said in the Navy statement.

“The U.S. and Australian P-8As will be able to operate with each other effectively and affordably for decades to come.”

In 2009 Australia signed a series of memoranda of understanding to work on the U.S. Navy on a single system that would meet both countries’ needs for anti-submarine warfare, anti-surface warfare and intelligence, surveillance and reconnaissance capabilities. India also bought into the program, and Boeing has delivered six of the eight P-8I variant aircraft ordered in a 2009 contract.

For the U.S. Navy, this most recent contract provides nine more P-8As in the second full-rate production lot, bringing the Navy’s total buy to 62, with 28 delivered so far. The service will eventually buy 117 total.