Kirby and Pentagon Press Secretary George Little last month announced restrictions to F-22 flight operations after 12 pilots reported hypoxia-like symptoms.
In response, Secretary of Defense Leon E. Panetta directed the retrofitting of automatic backup oxygen systems in the Raptor.
The Air Force is investigating the issue and providing monthly reports to Panetta.
In addition, all F-22 flights were ordered to remain near potential landing locations to enable quick recovery and landing should a pilot encounter problems during flight, Little said last month.
There are no plans to ground the aircraft, but Kirby said the Defense Department remains prepared for all possibilities.
“It’s a safety-of-flight issue,” he said. “Secretary Panetta understands that, and he’s not taking any options off the table with respect to the future of the aircraft.
“Right now the aircraft is performing very well in an operational setting and … we’re just going to continue to watch this as we move forward,” Kirby said.