Jakarta. The two pilots of the Indonesian airliner Batik Air who were both asleep for 28 minutes during a flight had been given a rest of at least one and a half days before the incident, according to the investigation results released on Sunday.

The plane was carrying 153 passengers when the incident occurred.

The pilot, aged 32, and co-pilot, 28, both Indonesian nationals, hold valid airline transport pilot licenses (ATPL) to fly the Airbus A320, according to a report by the National Transportation Safety Committee (KNKT), a copy of which was obtained by the Jakarta Globe.

The incident took place during a roundtrip flight between Halu Oleo Airport in Kendari, Southeast Sulawesi, and Soekarno-Hatta International Airport in Tangerang, Banten, on January 25.

The BTK6723 flight slightly deviated from its route due to the incident and it was very fortunate that it didn’t end up in a disaster.

Here's what we know so far about the incident:

Sleepy Co-Pilot
The plane took off from Soekarno-Hatta Airport at 3:14 a.m. Jakarta time, heading to Kendari. During the flight, the captain noticed that the co-pilot was visibly tired and allowed him to get some rest in the cockpit.

“The co-pilot slept for about 30 minutes,” according to the KNKT report.

The plane landed safely at Halu Oleo Airport at 7:11 a.m. local time, 30 minutes behind schedule on advice from the air traffic controller (ATC) due to unfavorable weather while awaiting the airport to resume its morning routine. Kendari’s time is one hour ahead of Jakarta.

Take Turn to Sleep
At 8:05 a.m. local time, the aircraft departed Halu Oleo for Soekarno-Hatta Airport, with the co-pilot taking charge of the flight. At 8:37 a.m., the pilot asked for permission to sleep, approved by the co-pilot.

The pilot woke up at 9:22 a.m. and asked the co-pilot if he would take some rest, to which the co-pilot declined. They chatted for about 30 seconds before the captain went back to sleep.

Meanwhile, the local area control center asked the crew to shift communication to the Jakarta ATC.

Upon receiving directions from Jakarta, the co-pilot was asleep for 10 seconds. Communications with the ATC resumed moments later, but then he fell asleep again, leaving the plane completely without an alert pilot while flying thousands of feet above the ground.

In 12 minutes after the last communication, the Jakarta ATC asked about their flight status but received no response. Traffic controllers attempted to call again, 28 minutes after the last conversation, and this time the pilot woke up and responded.

He soon realized that the plane was “not on the correct flight path” and woke up his co-pilot, KNKT said. He told the traffic controller that there had been issues with the radio but that they were okay by then.

The flight proceeded to Soekarno-Hatta and landed without any further incident.

Enough Rest Time
The pilot was given a rest period of 35 hours from the last flight before the January 25 incident, the report said.

He has a total flying time of 6,304 hours and 11 minutes and holds a valid first-class medical certificate with a medical limitation to wear corrective lenses.

“The last proficiency check was conducted on November 12, 2023, and the result was satisfactory,” according to the KNKT.

During the past seven days prior to the January 25 flight, he had flown for 16 hours and 31 minutes.

However, he had slept for just around two hours before departing to the airport to fly the Airbus early on January 25.

The mandatory health checkup showed his blood pressure and heart rate were normal, and he also tested negative for alcoholic drinks.

Reasons for Fatigue
The co-pilot holds a valid commercial pilot license to fly an Airbus A320 with a total flight time of 1,664 hours and 45 minutes. His certificate indicates that he has no medical limitations, with the last proficiency conducted on November 1, 2023, with satisfactory results.

He had been given a rest period of 53 hours before January 25, but the investigation revealed circumstances that may have led to fatigue.

He had month-old twin babies at home and was busy moving to a new house with his family during the rest period.

The co-pilot attempted to sleep early at around 7 p.m. before the January 25 flight but was disrupted several times as he helped his wife take care of the babies, KNKT said.

However, he passed the medical check on the spot and was deemed fit to fly the aircraft.

The report said that Batik Air’s internal safety procedures require cockpit checks every 30 minutes during the flight, but it fails to specify who is responsible for such a task.

Batik Air is a subsidiary of Lion Air, Indonesia's biggest budget airline.