A few months ago, Air Force leaders noticed some very strange behavior from pilots in the cockpit of F-22 Raptor fighters. Some pilots sounded like they were drunk on the radio; others couldn't even remember how to use the radio during flights. Lab tests revealed not alcohol in the pilots' blood, but a host of toxic chemicals including oil fumes, anti-freeze and even propane. The Air Force grounded the entire stealthy F-22 fleet on May 3rd and launched an investigation. This week, the Air Force Times reports that they're still stumped, which is not the best news for the fantastically expensive and problem-prone F-22s.

The Air Force has definitely figured out that toxins are making their way into the cockpit, but they don't know  how. The symptoms that the pilots were displaying resemble those of hypoxia, a condition due to a lack of oxygen. Captain Jeff Haney exhibited the similar symptoms just before he crashed and died in Alaska in November of 2010. Suspecting that the chemicals entered the cockpit through the jet's life support system, the Air Force is investigating the oxygen masks and pressurization systems, but they've yet to find the link.

One of the Air Force Times's sources wonders if pilots starting up the jets inside during bad weather might be causing a running-car-in-a-closed-garage effect:

Because of the harsh climate, pilots often start their jet engines inside a hangar before taking off. That could allow exhaust gases to be trapped in the building, sucked back into the engines, and ingested into the bleed air intakes that are located within the engines’ compressor sections that supply the OBOGS, sources said. The layout, sources added, is standard for modern jet aircraft.

But another source said that many of the hypoxia incidents have occurred well into flights or even during a day’s second mission, long after the plane has left the Elmendorf hangar.

Unable to fly, pilots are stuck in simulators and runway taxiing exercises for safety's sake. Investigators haven't given any clues to how close they might be to a solution, but if pilots are grounded more than 210 days, they all have to get retrained, inevitably an expensive option.

Expensive and problematic has become a trope for all things F-22-related. Just before the the toxin problem hit its tipping point, the jets were supposed to see their first combat action in Libya. Manufactured in Georgia and championed by Georgia Senator Saxby Chambliss, the jets lost the privilege of leading the first attacks over Libya after showing signs of communications and missile navigation issues. Meanwhile, folks at the Project on Government Oversight (POGO) are starting to wonder why the government is still supporting the program.

"Given the extraordinary cost of this aircraft and the myriad problems in maintaining it (you can’t use a plane if it’s grounded), is the F-22 too expensive and too difficult to use?" asked POGO's Director of Investigations Nick Schwellenbach earlier this month. "The oxygen system issue is just the latest fiasco in this program."

Schwellenback links to a Washington Post article from 2009 that reports an F-22 requires "more than 30 hours of maintenance for every hour in the skies, pushing its hourly cost of flying to more than $44,000." The government has so far sunk billions into the F-22 fleet.