French investigators have so far been unable to determine the composition of the flight crew on duty when an Air France Airbus A330-200 was lost over the South Atlantic last month.
The crew had been reinforced with a third pilot to meet flight-duty time regulations, and the aircraft's configuration included a crew rest area.
Recovery teams have retrieved 51 victims of the accident from the 228 occupants on board, the aircraft's captain among them.
Investigators have not established whether the captain was in the cockpit at the time of the accident. He had 1,747hr on type, all as captain, and 10,988hr in total.
The more experienced of the two co-pilots had 4,479hr on type, from 6,547hr in total, while the second co-pilot had 807hr on type from a total of 2,936hr.
In its interim report on the accident the Bureau d'Enquetes et d'Analyses states: "From the current state of the information gathered, it is not possible to determine the composition of the flight crew on duty at the time of the event."
The rest station on Air France A330-200s includes two beds and is located behind the cockpit.
While the reinforcing crew stays in the cockpit for departure and arrival, during the cruise each member of the crew must be able to rest for at least 1hr 30min continuously.
Under Air France procedures the captain determines the allocation of tasks before any prolonged absence from the cockpit, identifying the pilot who will replace him. He also specifies the conditions that would necessitate his return to the flight deck.