Two strange events on that flight prompted the FAA to open an investigation.

It started as a normal flight.

Go! Airlines flight 1002 took off from Honolulu on time at 9:25 a.m. last Wednesday on it's way to Hilo.

But as the plane neared Mauna Kea on the Big Island, at least one passenger on board noticed something was wrong.

"When I noticed we weren't descending I told my wife, she was sitting on the left, I mentioned to her I think something is kind of weird with this flight pattern," said passenger Derrick Lining.

Sources said air traffic controllers tried to contact the pilots for 25 minutes and got no response.

A radar track obtained by KGMB9 shows the plane stayed at 21,000 feet as it flew past the Hilo airport possibly still on autopilot.

Sources confirm the pilots went off track 15 miles out to sea before turning around and finally landing.

"We are investigating whether the pilot and copilot of an interisland go! Airlines flight fell asleep while the plane was in the air between Honolulu and Hilo," said FAA Ian Gregor.

Airline analyst Peter Foreman said it has happened before but never on such a short flight.

"For both pilots to fall asleep at 9 o'clock in the morning that seems pretty strange," said airline analyst Peter Foreman.

While he doesn't know what happened on that flight, he said the circumstances are unusual.

If for some reason, there are communications problems and a pilot can't reach air traffic controllers.

"You are going to query, you are going to get on different frequencies, you are going to try different radios and try everything to re-establish communications," Foreman said.

And he can't explain why a pilot would fly past an airport.

"Even if there was communications failure that jet should have started down for the destination and it didn't. So those pilots have a lot of explaining to do," Foreman said.

Click here for an update on this KGMB9 story

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