An impression of the Japan Super Interceptor depicts an aircraft armed with eight AIM-120 AMRAAM air-to-air missiles and a single long-range standoff air-to-surface weapon

Boeing has signed a direct commercial sale (DCS) agreement with Mitsubishi Heavy Industries (MHI) to support the upgrade program intended for the F-15J Eagle fleet, the U.S. company announced on July 28. The Japan Air Self-Defence Force (JASDF) intends to modify up to 98 of its current F-15J fleet to a "Japan Super Interceptor" (JSI) standard, with work set to start in 2022.

MHI, which built most of Japan’s F-15s under license from McDonnell Douglas (now Boeing), is the prime contractor for the JSI, with Boeing providing assistance and support in many areas. Under the agreement, Boeing will provide retrofit drawings, ground support equipment, and technical publications related to the modification of the first two aircraft. Support will be provided by local trading company Sojitz Corporation.

Japan decided to upgrade part of its Eagle fleet as a result of heightened tensions in the region, notably with China. Mirroring to an extent what the U.S. Air Force will be getting with the F-15EX, the JSI will have the new ALQ-239 digital electronic warfare systems, advanced cockpit displays, and the ADCP II mission system computer, which Boeing describes as the “world’s most advanced.” The aircraft will feature Raytheon APG-82(V)1 active electronically scanned array radar.

The initial DCS deal is part of a program worth around $4.5 billion approved by the U.S. State Department in October 2019. There will also be Foreign Military Sales (FMS) elements, for which Boeing is nominated as the prime contractor.

As with the F-15EX, the JSI is expected to be armed primarily with air-to-air missiles, but will also have the ability to carry large air-to-surface weapons. An officially released image shows a notional JSI armed with a Lockheed Martin AGM-158 Joint Air-Surface Standoff Missile. Alternatives could include the LRASM anti-ship missile, which is based on the AGM-158, and hypersonic weapons, development of which is underway in Japan.

Upgrading around half of the F-15J fleet is part of Japan’s plan to dramatically overhaul and expand the capabilities of the JASDF. The JSIs will augment the main fleet of Lockheed Martin F-35As, of which the first squadron has already formed. The initial purchase of 42 F-35As has been followed by a decision to buy another 63 F-35As and 42 F-35B short take-off/vertical landing aircraft. State Department approval for this follow-on batch of 105 aircraft was granted on July 9.