The US Navy efforts to diagnose the root cause of the problems with the Onboard Oxygen Generation System (OBOGS) of T-45 Goshawk jet trainer aircraft is at a dead end, according to USN Naval Air Systems Command (NAVAIR) chief Vice Admiral Paul Grosklags. Speaking at a US Senate panel on 13 June, Grosklags said the USN had not been able to discover a toxin or contaminant in the breathing gas. 

T-45 trainer fleet was grounded on 5 April this year for 12 days for investigation and resumed operations of the platforms by limiting the maximum cabin altitude to below 10,000 ft in order to be able to operate without using the OBOGS system. 

Grosklags stated that USN evaluated every single component in the breathing gas path, including all the piping, all the way from the engine up to the mask and the vests air crew wear and has subjected these parts to environmental condition extremes in excess of what it would ever expect to see in the aircraft and still has been unable to find what it would consider approximate cause of contamination. The service is now focused on adopting protective measures and warning mechanisms.