A recent investigation by Japan’s Board of Audit has revealed persistently low operational availability of the Maritime Self-Defense Force’s (JMSDF) P-1 maritime patrol aircraft, citing chronic engine issues and a growing shortage of replacement parts.
The aircraft, domestically developed and in service since 2013, was designed to enhance surveillance and intelligence-gathering capabilities across Japan’s surrounding maritime zones.
The P-1, developed by Kawasaki Heavy Industries, was intended to replace the aging fleet of U.S.-designed P-3C aircraft. While it offers extended endurance and modern surveillance equipment, its operational record has been hampered by mechanical failures and supply chain disruptions.
According to the Board of Audit’s findings, between fiscal years 2019 and 2023, only a fraction of the fleet could carry out missions without restrictions. As of September 2024, 35 P-1 aircraft had been deployed across Atsugi, Kanoya, and Shimofusa air bases, but many remained grounded or under repair.
One of the primary issues involves engine corrosion caused by salt exposure. The engines, manufactured by IHI, have suffered from material degradation that rendered several units inoperable. The audit also reported failures in key onboard electronics and weapons systems, further limiting mission readiness.
Another critical problem is the shortage of spare parts. Due to global semiconductor shortages, labor constraints, and shifts in the international supply chain, the time between parts orders and deliveries has lengthened. This has led to a reliance on “cannibalization,” the practice of removing parts from one aircraft to keep another operational.
In response to the audit, the Ministry of Defense issued a statement saying it would “take the findings seriously” and is pursuing measures to stabilize parts availability. According to the ministry, it aims to resolve the shortage through consolidated maintenance contracts by fiscal year 2027.
The P-1 program has already cost Japanese taxpayers approximately ¥1.77 trillion ($11.2 billion USD) through fiscal 2023. Total lifecycle costs are estimated to exceed ¥4 trillion ($25 billion USD) by the end of its service life in fiscal 2054.
The aircraft plays a central role in Japan’s maritime security, especially as neighboring states increase activity in regional waters. Earlier this month, both of China’s aircraft carriers — Shandong and Liaoning — operated simultaneously in the Pacific. In February, a Russian naval intelligence ship sailed through Japan’s contiguous zone near Miyazaki Prefecture for the first time.
The audit warns that the current low availability of the P-1 fleet could leave gaps in Japan’s maritime surveillance posture, especially as the country faces what officials describe as the most complex security environment since World War II.