Sleeping pilots? A communications breakdown in the cockpit? A medical emergency? Hijackers?

Fearing the worst, air traffic controllers alerted the military about a commercial jet flying from Honolulu to Hilo at 21,000 feet with 40 passengers that missed its landing and failed to respond to nearly a dozen calls.

Despite a silent cockpit on go! airlines Flight 1002 over a span of 17 minutes, fighter jets were never scrambled to assist or escort, raising questions about a possible breakdown in security measures.

"Didn't we learn our lesson from 9/11?" asked Joseph Gutheinz, a former inspector for the Federal Aviation Administration and the U.S. Transportation Department. "Why is it that there wasn't an interceptor up there trying to find out what was going on with that plane?

"If we don't get it now, what about next week when somebody does hijack a plane? All that tells you is that Hawai'i is wide open for a terrorist attack."

Flight 1002, which left Honolulu on Feb. 13 at 9:16 a.m., ended up overshooting Hilo International Airport by 15 miles, according to the FAA.

The pilots are being investigated by the FAA and the National Transportation Safety Board for possibly falling asleep on the brief, 214-mile flight. They also have been grounded by go!'s parent company, Phoenix-based Mesa Air Group.

In air traffic control recordings obtained Thursday by The Associated Press, the controller is heard repeatedly trying to contact the pilots and even talked to the pilot of another go! airlines flight in hopes of reaching Flight 1002.

"He was supposed to be landing at Hilo," the unidentified controller says. "I show him heading southeast-bound past Hilo. I'm worried he might be in an emergency situation."

Finally, about 44 minutes into the flight, the controller was able to establish radio contact and told the flight crew to change course and head back to Hilo, where they landed safely about 15 minutes later, according to a preliminary report by the NTSB.

"Air shuttle 1002, I've been trying to contact you for the last 90 to 100 miles. I understand you've passed Hilo. I'm going to turn you back to the northeast-bound to get you back to the Hilo airport. Is there some kind of emergency situation going on?"

The reply from the go! captain, who has not been identified by the airline: "Uh, no. We've just must have missed the handoff or missed the call or something."

None of Hawai'i Air National Guard's F-15s was alerted, said Capt. Jeff Hickman, spokesman for the Guard.

In fact, the Guard has not responded to any calls for emergency scrambles for civilian flights in Hawai'i since the 2001 terrorist attacks.

The Guard noted it only serves as responders, and decisions to scramble are made at a higher level.

Officials at the Hawai'i-based U.S. Pacific Command did not return an e-mail or three phone calls seeking comment on why the fighter planes were not scrambled or called.

The FAA said it promptly notified the Domestic Events Network, an interagency teleconferencing system established after the Sept. 11, 2001, terrorist attacks. The network allows the FAA to communicate with the Department of Defense and other agencies to coordinate a response to suspicious activities or possible air-related emergencies.

FAA spokesman Ian Gregor said his agency "reported it in an appropriate manner," and noted it cannot order fighter jets to scramble.

"I don't know how somebody can criticize a response to an incident when they have no idea what went on behind the scenes," Gregor said.