The Air Force is still working to find the root cause of the problem which was first reported our years and caused the aircraft to be grounded for four months last year.
Some of the “findings” of the [Scientific Advisory Board] to date include the fact that the Raptor’s onboard oxygen generation system (OBOGS) and emergency oxygen system were not classified as safety critical items, according to a document released by the USAF. Additionally, there is no backup system that automatically supplies oxygen to the pilot if there is a failure of the primary life-support system. Nor was there a requirement to inspect or maintain OBOGS components until recently.
So an issue no one originally thought much about has caused much trouble, which highlights the challenges of developing complex systems.