According to the aviation news site Aviation Herald, two Ethiopian Airlines pilots fell asleep and missed their landing while flying from Sudan to Ethiopia last Monday.

The passenger flight ET343, a Boeing 737-800, was flying from Khartoum to Addis Ababa when the pilots nodded off and flew past the runway, continuing their route.

According to the aviation news site, air traffic control attempted to contact the pilots several times but was unable to reach them. When the pilots flew past the landing zone, the autopilot disengaged, causing an alarm to sound, waking them up.

When the pilots regained consciousness, they rerouted the plane to Addis Ababa Bole International Airport, where they safely landed 25 minutes later, as shown on a FlightAware flight map.

Ethiopian Airlines did not confirm whether the pilots dozed off, but it did issue a statement Friday stating that the flight “temporarily” lost contact with air traffic control.

“The affected crew has been removed from service pending further investigation,” Ethiopian Airlines stated. “Based on the investigation findings, appropriate corrective action will be taken. Our top priority has always been and will always be safety.”

It is unknown how many passengers were on board.

Pilot fatigue is not a new phenomenon. According to a Frontiers study conducted last year, in-flight fatigue has been reported by 68 to 91% of commercial airline pilots.

The Southwest Airlines Pilot Association, the union representing Southwest Airlines pilots, warned airline executives earlier this year in an open letter that crew exhaustion has become dangerous.

“Acute and cumulative fatigue has become Southwest Airlines’ number one safety threat,” the letter stated.

The letter also discussed the dangers of flying while tired.

“The many negative effects of fatigue are well-documented,” the SWAPA wrote. “Impaired judgement, lack of concentration, reduced in-flight attention, and heightened emotional activity leading to poor cognitive processing, along with decreased reaction time and slower hand-eye coordination, to name a few.”

Ethiopian Airlines issued a press statement summarising the event, stating that the pilots had been “removed from operation pending further investigation.”

“Depending on the findings of the enquiry, suitable corrective action will be taken.” “Our primary goal has always been and will continue to be safety,” according to the press statement.