(CNN) -- A pilot's sleep disorder and a string of early mornings helped cause the crew of a commuter jet to fall asleep during a flight over Hawaii in 2008, federal investigators reported Monday.
The pilot and co-pilot of a Go! Airlines jet failed to respond to calls from air traffic controllers for 18 minutes during the February 2008 flight from Honolulu to Hilo and awoke to find they had overshot their destination by about 30 miles, the National Transportation Safety Board reported. The plane landed safely once the pilots awoke and resumed contact with controllers.
The 53-year-old pilot was later diagnosed with obstructive sleep apnea, which can cause daytime sleepiness.
"This condition likely caused him to experience chronic daytime fatigue and contributed to his falling asleep during the incident flight," according to the NTSB's report on the probable cause of the incident.
"In addition, the day of the incident was the third consecutive day that both pilots started duty at 0540 (5:40 a.m.)," the report continued. "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."
Go! is a subsidiary of Phoenix, Arizona-based Mesa Air Group. The company had no immediate response to the findings.
The Hawaii incident and a 2007 runway landing accident in Michigan that investigators blamed on pilot fatigue prompted a call by federal safety experts to scale back the maximum workday allowed for airline pilots and implement other "fatigue management" programs.