Air traffic controllers under scrutiny in plane collision probe.

(From Agence France Presse)

Investigators were at work examining wreckage from a mid-air collision over southern Germany that left 71 dead as air traffic controllers came under scrutiny for failing to avert the crash.

All 71 people aboard the two aircraft -- a Russian charter plane packed with student holidaymakers headed to Spain and a DHL Boeing 757 cargo plane -- were killed when they smashed into each other shortly before midnight Monday.

Quoting experts who examined the black box recovered from the Russian plane, the RIA-Novosti news agency reported from Moscow that Swiss air traffic controllers told the pilot to descend only 50 seconds before the collision, and that it did so within 25 seconds.

The crash apparently occurred as the Bashkirian Airlines plane bound for Barcelona and the mail service courrier plane took last-minute evasive action. It was the worst such air collision since two planes smashed into each other over India in 1996, killing 349 people.

"In my opinion, this was the fault of the air controllers," the director of Bashkirian Airlines, Nikolai Odegov, told reporters in Moscow's Domodedovo airport.

Bur the Swiss air traffic control service, Skyguide, said the pilot of the Tupolev-154 responded late to their repeated calls to descend from an altitude of 36,000 feet to a flight path 700 feet lower.