The F-22 Raptor, the Air Force’s most advanced weapons system, is the only fighter capable of "simultaneously conducting air-to-air and air-to-ground combat missions with near impunity," maker Lockheed Martin says on its website.

Now, if they could only get off the ground.

The Hawaii Air National Guard and active-duty Air Force showcased the stealth aircraft Friday at Joint Base Pearl Harbor-Hickam, where a groundbreaking was held for a $37.1 million maintenance hangar and squadron operations facility for the F-22s.

The Hawaii Air Guard has seven Raptors here, two on the mainland awaiting maintenance and 11 others that were supposed to fly in by the end of the year, officials said.

But an investigation into "hypoxia-like" symptoms — meaning not getting enough oxygen — experienced by some pilots elsewhere has left all Raptors in the Air Force inventory on stand-down since early May with no end to the grounding in sight.

Oxygen-generation systems continue to be looked at, the Air Force’s Pentagon office said.

About 200 people, including Gov. Neil Abercrombie, attended the groundbreaking for the new 77,500-square-foot hangar and operations facility, which the Guard said will allow it to demolish nine older buildings. The new hangar will be able to house six F-22s.

Honolulu-based Watts Constructors will be involved in building the new facility.

President Denny Watts said "jobs of this size make so much more impact" on work for prime contractors, subcontractors and vendors. He expects 50 and 60 workers to be on the job site.

F-22 improvement projects at Hickam totaling $156 million are expected to be completed through the next four to five years, officials said.

The Hawaii Air National Guard had been flying the Raptor since last summer in partnership with the active-duty Air Force and was steadily building up the squadron of aircraft.

Hawaii Adjutant General Maj. Gen. Darryll D.M. Wong acknowledged after the groundbreaking that there has been some pilot frustration with the inability to fly the stealth jets.

"I think for the pilots, it’s kind of like you just learned to drive a really fast car, and then they took the keys away from you," Wong said.

Wong, head of 5,500 Hawaii National Guard Army and Air Guard members, said he is not sure what the stand-down will do to the arrival schedule of the remaining 13 Raptors.

The grounding also has ramifications for pilot training and readiness. Mainland training schools have been suspended, he said.

"The Air Force, along with figuring out how to fix this airplane, will also have a plan forward on how to take the pilots that have been grounded and how to systematically get them back flying again," Wong said.

Some bases have F-22 simulators. Hickam doesn’t have one yet, he said.

"So whether these people go back to the mainland somewhere and get into the simulators and then get back into the airplane here is still yet to be determined," Wong said.

Maintenance personnel, on the other hand, have been able to "really get into the airplane and learn it," Wong said.

The Air Force said Thursday it is continuing to review all of its aircraft equipped with oxygen-generation systems, but said the F-22 is the only grounded airplane.

An Alaska F-22 pilot died in November when he lost control of his jet during training. The jet crashed about 100 miles north of Anchorage.

A team led by retired Air Force Gen. Gregory Martin will examine systems identified in reported incidents, including pressurization systems and mask and cockpit oxygen levels, the service said.

Air Force Times, quoting unnamed sources, said carbon monoxide might have entered the cockpit of jets whose engines were started inside hangars at Elmendorf Air Force Base in Alaska, where most of the hypoxia incidents have occurred.

Wong previously said there were no cases of hypoxia reported by Hawaii pilots.