French and Brazilian authorities are now in a race against time to recover the black box flight data recorders from crashed Air France flight AF447.

Brazilian authorities have confirmed that two debris fields covering a five kilometer strip were found about 650 km (400 miles) northeast of the Fernando de Noronha Islands, an archipelago 355 kilometers (220 miles) off the northeast coast of Brazil.

As memorial services get underway in Paris and Brazil, investigators are now in a desperate race against time to find and recover the flight data recorders from the doomed aircraft in an attempt to determine what caused a near-new aircraft to plunge from the sky.

Brazilian Defence Minister Nelson Jobim said locating the flight recorders could take a long time as it is possible that they are already on the ocean floor at a depth of about three kilometres (1.86 miles)

Experts say the devices can emit signals from great depths, but they usually only last for about a month.

A French ship is on its way to the zone, carrying two mini-submarines capable of operating at depths of 6,000 metres (19,700 feet), which is also the limit aircraft black boxes can survive for up to 30 days.

But any recovery will be extremely tricky, not only because of the depth, but also because of powerful currents and storms in the zone.

“To find the plane, you’ll need ships equipped with a special sonar, and possibly also rescue submarines… it’s an enormous undertaking,” Commander Ronaldo Jenkins, safety coordinator for Brazil’s airline association, said.

Air France flight AF447 departed Brazil’s Airport do Galeao in Rio de Janeiro on Sunday at 2230 GMT for Paris and was last heard from flying at an altitude of 10,600 meters (35,000 feet) at 0133 GMT Monday.

The relatively new Airbus A300-200 jetliner was carrying 126 men, 82 women, seven children and a baby – plus a highly experienced 12-person crew.