SEA08IA080

The captain and first officer inadvertently falling asleep during the cruise phase of flight. Contributing to the incident were the captain's undiagnosed obstructive sleep apnea and the flight crew’s recent work schedules, which included several consecutive days of early-morning start times.

go! flight 1002 departed for its destination about 0916 Hawaii standard time. About 0930, the captain transmitted to air traffic control (ATC) that the flight was climbing through 11,700 feet to its cruise altitude of flight level (FL) 210 (approximately 21,000 feet mean sea level.) The controller acknowledged the transmission and cleared the flight to proceed to an intersection along the flight route located about 29 miles north-northwest of the destination airport, and the flight crew acknowledged. At 0933, during cruise flight, the controller repeated the navigational clearance, which the flight crew acknowledged, and the airplane turned in accordance with the clearance. At 0940, the controller instructed the flight to change radio frequencies, and there was no response. The controller continued to try to contact the flight crew multiple times but received no reply. At 0951, the airplane crossed the intersection that was its clearance limit then turned southeast toward the destination airport without descending, which is consistent with the airplane being on autopilot. The controller handling the flight asked another controller to attempt to contact the flight crew on a different frequency, but there was still no response, and the flight proceeded on a southeasterly heading at FL 210. About 0955, the flight crossed over the destination airport and continued on a southeasterly course without changing altitude or heading. Two separate airline crews in the area attempted to contact the incident crew, but neither flight crews’ attempts were successful. About 0958, when the flight was about 26 nautical miles southeast of the destination airport, the captain contacted the controller with an abbreviated call sign (“Ah HCF ten zero two”), and the controller asked if the flight crew was experiencing an emergency. The captain responded, "No, we must have missed a hand off or missed a call or something." The controller then issued instructions for the flight to return to the destination airport, with which the flight crew complied. The flight arrived without further incident about 1015. The captain and first officer both reported to their company that they had unintentionally fallen asleep in flight. The fact that both pilots fell asleep during the midmorning hours, a time of day normally associated with wakefulness and rising alertness, indicates that both pilots were fatigued. The captain had undiagnosed severe obstructive sleep apnea, which was diagnosed during a medical evaluation shortly after this incident and for which symptoms (such as snoring) and risk factors (such as obesity) were present before the incident. This condition likely caused him to experience chronic daytime fatigue and contributed to his falling asleep during the incident flight. In addition, the day of the incident was the third consecutive day that both pilots started duty at 0540. This likely caused the pilots to receive less daily sleep than is needed to sustain optimal alertness and resulted in an accumulation of sleep debt and increased levels of daytime fatigue. The first officer stated he needed between 7.5 and 8 hours of sleep per night to feel rested. He estimated that he had spent about 7 hours 25 minutes in bed the night before the incident, and about 6 hours 55 minutes in bed during each of the previous two nights. Thus, the first officer’s self-reported sleep history indicated an accumulated sleep debt of between 1 hour 15 minutes and 2 hours 45 minutes in the 72 hours before the incident. The first officer’s reduced sleep probably resulted from the flight crew’s recent work schedule. The effect of early start times on sleep is well documented. A 1998 National Aeronautics and Space Administration Report, “Flight Crew Fatigue II: Short-haul fixed wing air transport operations,” for example, concluded that requiring early report times makes it more difficult for crewmembers to obtain adequate sleep. Further, a 1998 report published by North Atlantic Treaty Organization Research and Technology Organization (formerly AGARD), “Early starts: Effects on sleep, alertness, and vigilance,” concluded that pilots reporting before 0600 had a significantly shorter total sleep time, impaired sleep quality, and impaired performance both pre-flight and at top of descent. The pilots also were flying eight legs a day, requiring many takeoffs and landings, which are high-workload phases of flight. The incident pilots’ lack of adequate sleep, together with the low workload associated with the cruise phase of the flight, likely contributed to the pilots inadvertently falling asleep.

HISTORY OF FLIGHT At 0916 on February 13, 2008, a Bombardier CL-600-2B19, N651BR, operated by Mesa Airlines as Go! Flight 1002 departed Honolulu International Airport (HNL), Honolulu, Hawaii, on a regularly scheduled domestic, passenger flight using the call sign Air Shuttle Flight 1002 (ASH1002). About halfway through the flight, the pilots of ASH1002 stopped responding to air traffic control communications. While out of radio communications, the flight passed over its destination airport, General Lyman Field (ITO), Hilo, Hawaii, at cruise altitude. After traveling 26 nautical miles beyond ITO on a constant heading, the flight crew resumed radio communications with air traffic control and returned to land at ITO. The airplane was not damaged and the captain, first officer, flight attendant, and 40 passengers were not injured during the event. The flight was conducted in accordance with 14 Code of Federal Regulations (CFR) Part 121. An instrument flight rules (IFR) flight plan was on file and activated during the flight. The first officer was assigned the role of the flying pilot. The flight crew's communications with air traffic control during departure from Honolulu had been routine. About 0930, the captain had contacted Honolulu Control Facility (HCF) and informed the facility that ASH1002 was climbing through 11,700 feet to its cruise altitude, Flight Level 210. HCF acknowledged this transmission and cleared the flight to proceed direct to the PARIS intersection, near the big island of Hawaii. The captain acknowledged the clearance but the flight did not change course. About 0933, HCF again cleared ASH1002 direct to the PARIS intersection. The captain acknowledged the instruction a second time, and the flight's track turned toward PARIS. Both pilots later stated that soon after they received this clearance they inadvertently fell asleep in the cockpit. The captain stated, "Working as hard as we had, we tend to relax." He further stated, "We had gotten back on schedule, it was comfortable in cockpit, the pressure was behind us. The warm Hawaiian sun was blaring in as we went eastbound. I just kind of closed my eyes for a minute, enjoying the sunshine, and dozed off." The first officer said he entered a sleep-like state from which he could "hear what was going on, but could not comprehend or make it click." At 0940, as the flight was crossing the island of Maui. HCF instructed ASH1002 to change radio frequencies, but the flight crew did not respond. For the next 18 minutes, HCF attempted to contact ASH1002, but received no replies. About 0951, ASH1002 reached the PARIS intersection and turned southeast toward the Hilo VOR. The HCF controller who was handling the flight asked another HCF controller to contact ASH1002 on a different radio frequency. The other controller made the attempt, but received no reply. At 0955, ASH1002 crossed the Hilo VOR. It continued southeast at Flight Level 210, crossed the northeast coast of Hawaii and flew out over the open ocean. HCF asked another Go! flight crew to try to contact ASH1002 on a company radio frequency. The flight crew made the attempt, but received no reply. In addition, a Continental Airlines flight attempted to contact ASH1002 on an emergency frequency, but was also unsuccessful. About this time, the first officer awoke. Realizing the airplane was off course, he noted that 4,500 pounds of fuel remained. He estimated that this amount would last an hour and a half. Next, the first officer woke the captain and told him air traffic control was attempting to contact the flight. About 0958, the captain contacted HCF, stating, "[unintelligible] HCF ten zero two." HCF asked the captain if the flight crew was experiencing an emergency situation, and the captain replied, "No, we must have missed a handoff or missed a call or something." HCF then issued vectors for ASH1002 to return to ITO, and the flight crew complied. The flight arrived at 1015. As ASH1002 arrived at ITO, air traffic controllers directed the captain to contact them by telephone. After the airplane was parked at the gate, the captain instructed the first officer to prepare the airplane for its next flight while he disembarked and called the FAA. The captain told FAA personnel by telephone that ASH1002 had lost radio communications because the flight crew had selected an incorrect radio frequency. FAA personnel informed the captain that they intended to report the incident to Mesa Airlines. After his telephone conversation with the FAA, the captain returned to the airplane and had a discussion with the first officer about whether they should operate the next flight. The pilots agreed that it would be safe for them to do so because they were feeling very alert as a result of the incident. According to company records, they departed ITO for HNL on the incident airplane at 1028, using the call sign ASH1044. During the flight to HNL, the pilots discussed the incident further and they decided to remove themselves from duty upon arrival. ASH1044 arrived at HNL at 1118. After parking at the gate, the captain arranged for a reserve crew to operate the next flight he had been assigned to fly with the first officer. Next, the captain called the airline’s scheduling office to inform the company that both he and the first officer were removing themselves from duty for the rest of the day. The captain's telephone call was transferred to a chief pilot who requested an explanation for the flight crew's decision. The captain declined to provide an explanation on the telephone. A few hours later, however, he submitted a written report to Mesa Airlines explaining that he and the first officer had fallen asleep on ASH1002 during the cruise phase of flight. PERSONNEL INFORMATION Flight Crew Captain The captain, age 53, held an airline transport pilot (ATP) certificate for airplane multiengine land, and commercial privileges for airplane single-engine land. He possessed type ratings in the following airplanes: BA-3100, BE-300, BE-1900, CL-65, DHC-8, and SA-227. His pilot certificate carried the following limitation, "BE-300, BE-1900, SECOND-IN-COMMAND REQUIRED." Company records indicated that the captain had completed his last recurrent training on July 19, 2007, his last line check on December 5, 2007, and his last proficiency check on January 4, 2008. The captain had worked as an airline pilot for over 20 years. Air Midwest hired him as a pilot on October 7, 1987. Mesa Airlines acquired Air Midwest in 1991, and the captain became an employee of Mesa Airlines on September 3, 1997. At that time, he was a captain on the Beech 1900D. On September 16, 1997, he transitioned to the position of captain on the de Havilland DHC-8, and on July 23, 1998, he transitioned to the position of captain on the CL-65. The captain's statements and company records indicated that he had between 20,000 and 25,000 hours of flight experience, including 8,000 hours as pilot-in-command in the CL-65. The captain reported 830 flight hours in the last 12 months, 415 hours in the last 6 months, 207 hours in the last 90 days, 76 hours in January 2008, and 38 hours during the period February 1-12, 2008. The captain resided in Kennett, Missouri and had been based in the company's Nashville, Tennessee domicile. At the time of the incident, he was temporarily assigned to Mesa's Kahului, Hawaii domicile. This temporary assignment had begun January 13, 2008 and was originally scheduled to end February 9, 2008. Near the end of this period, however, the temporary assignment was extended for an additional 28 days. The captain's activities in the three days preceding the incident were as follows: • On Sunday, February 10, 2008, he reported for duty at OGG at 0740, flew 4 legs and went off duty at OGG at 1445. He reported going to sleep between 2030 and 2100, and described his quality of sleep as "probably good." • On Monday, February 11,