The Indonesian defense ministry and Boeing (BA.N) have agreed to sell 24 F-15EX fighter planes to help modernize the Southeast Asian country’s aging fleet, according to the government and the firm.

Officials from the ministry and a Boeing official signed the memorandum of agreement on Monday at Boeing’s St. Louis, Missouri, site, according to Boeing, but the deal is still subject to US government clearance.

“This state-of-the-art fighter will protect and secure our nation with its advanced capabilities,” Indonesian Defence Minister Prabowo Subianto said, according to Boeing’s statement.

Boeing and the defence ministry did not provide details on the deal’s value.

The F-15EX is the most advanced version of the F-15, with digital fly-by-wire flight controls, a new electronic warfare system, a digital cockpit, and the latest mission systems and software capabilities, Boeing said.

Prabowo and his U.S. counterpart, Lloyd Austin, discussed the planned procurement during Austin’s visit to Jakarta last year.

Indonesia has increased its defence spending in recent years to overhaul its fleet, which includes U.S-made F-16 and Russian Sukhoi Su-27 and Su-30 jets.

This year, Jakarta bought 42 Dassault (AM.PA) Rafale fighter jets for $8.1 billion.

It has also purchased 12 used Mirage 2000-5 fighter jets in an $800 million deal that drew criticism as the aircraft were considered too old.

Last year, the U.S. has also approved the potential sale of F-15ID aircraft and related equipment to Indonesia in a deal valued at up to $13.9 billion.

“After Rafale, the F-15 will make Indonesia a strong nation as we keeps building a mature defence diplomacy,” the defence ministry spokesperson said.