The US Navy’s commander of Naval Air Forces allowed the service’s T-45 Goshawk trainer jets to return to flight 17 April, after US Naval Air Systems Command (NAVAIR) temporarily grounded the fleet in light of persistent oxygen issues on the aircraft.

Earlier this month, more than 100 US Navy instructor pilots boycotted he T-45 flights until high-level Navy officials address the jets’ oxygen system issues. Pilots should resume operations early next but will be limited to flights under 10,000 feet, according to a 15 April NAVAIR statement. Although the on board oxygen generator system (OBOGS) is not needed at that altitude, pilots wear the mask in training and the communications mic is already established in the mask, a NAVAIR spokeswoman said in an email to FlightGlobal. The connection between the mask and the helmet reduces risk in case of ejection and in the event of an emergency, pilots can hook back into the oxygen, she adds.

Instructor pilots will conduct warm-up flights and will brief other pilots and students on the modified equipment.

"We will be able to complete 75% of the syllabus flights with the modified masks while we continue the important engineering testing and analysis at PAX River [Naval Air Station Patuxent River, Maryland] to identify the root cause of the problem,” Vice Adm Mike Shoemaker says in a 15 April statement. “This will remain our top safety priority until we fully understand all causal factors and have identified a solution that will further reduce the risks to our aircrew."

The OBOGS represent a persistent problem for the Navy’s T-45, EA-18Gs and F/A-18F/Gs and hypoxia has plagued the service’s fleet of T-45s for years now.

The Navy is continuing to work with flight surgeons, physiologists and toxicologists to identify the root problem, Shoemaker says. Recently, an independent review team from NASA visited Pax River as part of ongoing review of physiological episodes.