Two pilots of an Indonesian airline have come under fire after an incident report revealed they both fell asleep during a January flight with more than 150 people on board. The pilots were unreachable for roughly half an hour, waking to find that the plane had veered off course, the report said. 

The incident occurred on a roundtrip Batik Air Indonesia flight between Halu Oleo Airport in Kendari and Soekarno-Hatta International Airport in Jakarta on January 25. During preparation for the first leg of the flight from Jakarta to Kendari, the second-in-command pilot – a 28-year-old with roughly 1,600 hours of flying time – told the pilot in command that he did not have proper rest, according to a report by Indonesia's National Transportation Safety Committee. The commanding pilot, a 32-year-old with roughly 6,300 hours of flying time, allowed the secondary to rest during that leg of the trip for about half an hour. 

On the flight back to Jakarta, which had 153 passengers and four flight attendants on board, the commanding pilot asked the secondary – who napped during the first leg – if he could take a turn to rest, which was granted. A little while later, the pilot woke up and asked the other pilot if they wanted to nap, which they declined. 

About 20 minutes later, the incident report states the second pilot "inadvertently fell asleep" as they were roughly 36,000 feet in the air. 

Air traffic controllers and other pilots attempted to get in contact with the napping pilots to no avail. Then 28 minutes after the last recorded transmission, the commanding pilot woke up and was immediately "aware that the aircraft was not in the correct flight path." 

"The PIC [pilot in command] then saw the SIC [second in command] was sleeping and woke him up," the report says. "About the same time, the PIC responded to the call from another pilot and Jakarta ACC. The PIC advised the Jakarta ACC that BTK6723 experienced radio communication problem and currently the problem has been resolved. The flight then continued and landed at Jakarta uneventfully." 

Investigators said nobody was injured and the aircraft was not damaged. 

While the unnamed primary pilot on the flights had a rest period of 35 hours prior to the incident that involved exercise, visiting family and exercise, the secondary pilot on the flights, who was not named in the report, had 53 hours of rest time. 

According to the report, the secondary pilot is also a new father with month-old twins who, two days before the flight, moved houses. He told investigators that the day before the flight, he "had to wake up several times" to help care for his children and that he "felt his sleep quality had degraded" in the process. 

Batik Air said Saturday that the two pilots have been suspended, according to AFP. 

The Safety Board has recommended measures to prevent such incidents from happening again. One of those recommendations is further development of Batik Air Indonesia's personal checklist for pilots, which is meant for pilots to check themselves for illness, impairing medications, stress, alcohol, fatigue and their emotional state before flying. 

"The absence of detailed guidance and procedure might have made pilots unable to assess their physical and mental condition properly," the incident report says. "Therefore, KNKT recommends Batik Air Indonesia to develop detailed guidance and procedure for ensuring that the IM SAFE personal checklist can be used to assess pilot physical and mental condition properly."

The cockpit of the plane is also supposed to be checked every half-hour, but the investigation found that there was an "absence of detailed procedures" that "might have made the cockpit check policy unable to be implemented properly." 

The airline said it "operates with adequate rest policy," according to AFP, and that it is "committed to implement all safety recommendations." 

In:
• Indonesia
• Airlines

Li Cohen is a social media producer and trending content writer for CBS News.