Africa’s biggest carrier Ethiopian Airlines said it has suspended two pilots who reportedly fell asleep and missed their landing during a flight from Khartoum to Addis Ababa.

The plane overshot the runway at Bole International Airport in the Ethiopian capital on Monday before landing safely, according to flight-tracking website FlightAware.

Independent website The Aviation Herald said the pilots fell asleep during the flight and were only woken up by an alarm triggered when autopilot mode disconnected.

The plane circled back to land 25 minutes later, flight data showed.

Ethiopian Airlines said on Friday that flight ET343 had temporarily lost communication with air traffic control but landed safely after it was restored.

“The concerned crew have been removed from operation pending further investigation,” the airline said in a statement without saying if the pilots had been asleep.

“Appropriate corrective action will be taken based on the outcome of the investigation,” it added.

The flight between the two capitals normally takes less than two hours.

London-based aviation analyst Alex Macheras described the incident as “deeply concerning”, blaming it on widespread fatigue that poses a major threat to air safety.

“Pilot fatigue is nothing new, and continues to pose one of the most significant threats to air safety – internationally,” he posted on Twitter.

In March 2019, a Boeing 737 MAX operated by Ethiopian Airlines crashed six minutes after takeoff into a field southeast of Addis Ababa, killing all 157 people on board.

The disaster, five months after a similar crash in Indonesia, triggered the global grounding of the jet for 20 months, before it returned to service in late 2020.

Ethiopian Airlines, a 100 percent state-owned company, reported turnover of $3.51 billion for the 2020-2021 fiscal year.