TOKYO -- In the weeks since a Japanese F-35A stealth fighter jet crashed into the Pacific Ocean, the U.S. and Japan have not yet found either the plane or the cause of the incident. But it could be linked to a system that has bedeviled the American military for years.
All F-35s have onboard oxygen generation systems, or OBOGS, which draw oxygen from the surrounding air and supply it to the pilot at the high concentration necessary to operate at high altitudes. The U.S. Air Force, Navy and Marine Corps have used OBOGS for more than three decades, in models including the F-16 and F/A-18 as well as certain training planes.
But since the U.S. began using OBOGS in the F-22 in 2008, there have been more than 20 cases of F-22 pilots experiencing symptoms indicating a lack of oxygen, apparently due to problems with the system. An F-22A crashed in November 2010 in an incident that may have resulted from an oxygen shortage.
Low levels of oxygen in the bloodstream -- known as hypoxia -- can cause sweating, headaches and dizziness, followed by vision problems and trouble making decisions, and eventually loss of consciousness. After the 2010 crash, the U.S. military temporarily stopped using OBOGS in the F-22 while it worked to address the issue, in part by replacing components in the system.
But the problem persisted in multiple jet models, including the F-35A. The military has not worked out the cause but reportedly has increased the emergency oxygen supply provided to pilots in case the OBOGS fails, among other precautions. Put bluntly, it is employing every trick it can think of to keep using the system.
With the Japan incident, the Air Self-Defense Force pilot called a halt to his training exercise just before the crash. This suggests that he realized something was wrong, after which the situation quickly deteriorated. That would fit with hypoxia caused by an OBOGS malfunction.
Such problems are a risk in the modern era. These days, all aircraft, civilian or military, are filled with electronics requiring complex software to run. As such, new planes must be put through a series of test flights to find and correct any problems in the code.
Test pilots, as well as the first pilots to operate new models after their rollout, must fly without knowing whether bugs might still lurk in their planes' programming. The task is a dangerous one.
The ASDF grounded all of its F-35As after the crash. At this point, it is impossible to tell whether the OBOGS might have been involved in the incident. But whether or not this turns out to be the case, given the long-running issues with the system in the U.S., Japan must also consider it suspicious.
But the ASDF cannot simply modify the planes to remove the OBOGS and use liquid-oxygen systems like those in the F-15, its current mainstay, because that would break the terms of its deal with Washington. This is a major downside to buying foreign jets.
There is one other concern. In June 2017, the USS Fitzgerald, an American destroyer equipped with the Aegis missile defense system, collided with a Philippine containership off the Japanese coast, killing seven people on board. The captain and another officer were court-martialed for criminal negligence. But the U.S. Navy recently made the unusual decision to withdraw the charges.
Like modern fighter jets, Aegis-equipped vessels are full of electronics. The accident prompted speculation that the Fitzgerald could have been hacked or hit with an electromagnetic pulse attack that caused systems to malfunction.
With military secrets involved, the truth remains a mystery. But the strange decision to withdraw charges over an incident that caused multiple deaths raises the possibility that hacking was found to have been involved, leading the military to conclude that the officers were blamed in error.
There are worries that the F-35A and the F-22 could be hacked -- perhaps during system updates -- to plant the seeds for future software problems. The U.S. military is believed to be looking into this risk with respect to the OBOGS malfunctions.
A national security source said of a recent piece on the American scramble to keep the F-35's secrets safe from Russia and China: "I agree with it, but the situation is more serious than that," the source said. What that could mean remains a mystery of its own.