Lawmakers are growing frustrated with the Air Force's inability to figure out why pilots suffer from oxygen deprivation while flying the F-22 Raptor and are raising the possibility of congressional hearings into the matter.

"I am not [quite] ready to come to that conclusion yet ... [but] my patience is wearing thin," Sen. Mark Warner Mark Robert WarnerFBI director casts doubt on concerns over mail-in voting fraud Democrats call for declassifying election threats after briefing by Trump officials It's time to upgrade benefits MORE (D-Va.) told reporters Tuesday in response to a question on whether he or Rep. Adam Kinzinger (R-Ill.) planned to call Air Force leaders up to Capitol Hill to testify.

"We are not taking anything off the table," the Virginia Democrat added during Tuesday's conference call, adding his office would be contacting Defense Secretary Leon Panetta in the coming days.

The scrutiny comes after two more incidents came to light of Raptor pilots experiencing a lack of oxygen during flight.

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Last Friday, an F-22 pilot based at Hickam Air Force Base in Hawaii signaled an "in-flight emergency" during a routine mission aboard the Raptor, according to a letter sent by Warner and Kinzinger to Air Force Secretary Michael Donley on Tuesday.

The emergency call was sent out after the pilot began to experience "restricted airflow" from the Raptor's on-board oxygen system, according to the letter.

A second incident occured on May 31, when an F-22 crash-landed onto the runway at Tyndall Air Force Base, Fla., without deploying its landing gear — an error that could have been the result of the pilot suffering from oxygen deprivation.

The two incidents took place after Defense Secretary Leon Panetta placed a number of restrictions on F-22 operations and ordered the Air Force to provide monthly updates on how they were resolving oxygen issues aboard the fighter.

Despite these efforts, the ongoing troubles within the Air Force's Raptor fleet represent "a never-ending saga" that service and Pentagon officials cannot seem to solve, according to Warner.

"I thought we were on to something ... but this is an issue that has not been tackled,"" Kinzinger added regarding DOD's ongoing efforts to investigate the cause of the ongoing oxygen system problems on the F-22.

"Each incident ... represents a potential accident" or loss of life, he added.

Air Force officials have yet to disclose the details of the recent Raptor incidents in Hawaii or Florida, according to the two lawmakers.

However, officials from the Air Force's congressional liaison office have been briefing members of Congress on the July 6 incident in Hawaii, an Air Force spokesman told The Hill on Tuesday.

Service officials have yet to disclose details on the crash landing in Florida, as the incident is still under investigation by Air Force officials, according to the spokeswoman.

That said, the information that has been provided on past oxygen deprivation incidents going back to 2008 have been less than satisfactory, according to Warner.

"We want the Air Force to get this right ... but [also] want our questions answered," he said.

In June, Warner and Kinzinger released data on the F-22’s oxygen problem, showing that the plane has had 10 times more incidents of oxygen deprivation than any other Air Force aircraft.

There were 26 incidents of hypoxia or hypoxia-like symptoms per 100,000 flying hours, the lawmakers said, according to information provided by Air Force at the time.

The entire F-22 was grounded last year as the service tried to pinpoint the oxygen problem, but flights were resumed without the source being located.

In May, two F-22 pilots appeared on “60 Minutes” to say they had refused to fly the planes for safety concerns. They had gone to the Warner and Kinzinger for whistle-blower protection.

--The story was updated at 4:16pm to include comments from an Air Force spokeswoman