Photo/Illutration An F-15 fighter jet (Provided by the Air Self-Defense Force)

The estimated cost of equipping the Air Self-Defense Force’s F-15 fighter jets with “standoff missiles” capable of hitting enemy bases has surged to more than 1 trillion yen ($6.7 billion), sources told The Asahi Shimbun.

That is more than 1.5 times the Defense Ministry’s initial estimate, and the increase will likely delay deployment of the upgraded aircraft, currently scheduled for fiscal 2027, the ministry sources said.

The upgrade plan is a pillar in the Self-Defense Forces’ efforts to strengthen its response capabilities to China’s maritime expansion.

The U.S. military started operating the F-15 in the 1970s.

Of the 200 F-15s owned by the ASDF, 68 relatively newer models will be upgraded with the Joint Air-to-Surface Standoff Missile-Extended Range (JASSM-ER) with a range of about 900 kilometers.

The plan also calls for installing new radar and electronic warfare equipment on the fighter jets.

Mitsubishi Heavy Industries Ltd. will upgrade the aircraft with technical cooperation from Boeing Co. of the United States. The F-15s are expected to be operational until around 2050.

In fiscal 2021, the Defense Ministry calculated the estimated cost of upgrading and testing the 68 aircraft at 646.5 billion yen.

However, rising expenses for development tests, the weakened yen and inflation prompted the ministry to re-estimate the cost. It was 1.16 trillion yen as of March this year.

The F-15 upgrade plan began in fiscal 2019, and it was revised in fiscal 2021 due to ballooning costs.

But even under the revised plan, costs continued to soar.

Since spring, the ministry has informed manufacturers and others involved in the project that “deployment of the upgraded aircraft, which had been scheduled for fiscal 2027, is expected to be delayed,” according to sources.

They said there is a possibility the fighter jets may not be ready by fiscal 2028.

On the other hand, the standoff missiles to be mounted on the F-15s have been budgeted since fiscal 2023 and are expected to be deployed in fiscal 2027 or later.

“Even if there are missiles, the fighter aircraft that will carry them may not be ready” by fiscal 2027, a ministry official said.

The upgrade is being conducted under the framework of the U.S. government’s Foreign Military Sales program. This allows the U.S. government to act as the negotiating intermediary based on the intentions of U.S. manufacturers and to deal with the Japanese government.

Before the upgrade, “initial expenses” are required for things such as designing the equipment to Japanese specifications and building facilities for the work. Most of these expenses are paid to the U.S. side.

The Defense Ministry had appropriated 183.7 billion yen as initial expenses through the fiscal 2024 budget.

Although no funds were earmarked for fiscal 2025, a senior ministry official said Japan and the United States were still working out the total amount of initial expenses and that the appropriation has not been completed.

“Once the amount is finalized, we will promptly allocate the rest of the initial expenses,” the official said.

In addition, 91.9 billion yen had been appropriated for the upgrade of 20 ASDF aircraft in the fiscal 2023 budget.