The incident occurred in January on a return flight from Kendari, in the Indonesian province of Southeast Sulawesi, to the country’s capital, Jakarta.
The captain of the Batik Air Airbus A320 aircraft, 32, took a nap after getting permission from his copilot while the plane was at a cruising altitude of 36,000 feet.
Around 45 minutes later, the captain woke up and offered to let the copilot, 28, rest, but they declined, and the captain fell back asleep.
The first officer spent roughly the next 20 minutes communicating with air traffic controllers and flight attendants before they “inadvertently” also fell asleep, per the report.
Twenty-eight minutes after the copilot’s last recorded transmission, the captain woke up and saw that his second in command was asleep and that they had flown off-course.
After waking them, the captain answered another pilot’s call and air traffic controllers, claiming they had suffered a “radio communication problem.”
The plane later landed in Jakarta without any further issues.
Many long-haul flights have relief pilots to ensure each pilot is sufficiently rested when they take the controls.
On short-haul flights such as the Batik Air flight, which takes roughly two hours and 40 minutes, controlled rest periods are more common: One pilot can briefly catch some shut-eye while the other continues monitoring the controls.
It is designed to help manage fatigue and improve safety.
According to the KNKT report, the second in command had not rested sufficiently the night before the flight.
Investigators did not reveal the pilots’ identities but said both were Indonesian nationals.
The report acknowledged “the safety actions taken by the aircraft operator and considered that the safety actions were relevant to improve safety,” but it did make some safety recommendations over adding guidance on checking pilots’ physical and mental conditions and carrying out cockpit checks.
Batik Air said in a statement that it “operates with adequate rest policy” and that it was “committed to implement all safety recommendation,” the MailOnline reported.
Business Insider has reached out to Batik Air for comment.
