Officials from the Russian government, Bashkirian Airlines and Moscow's Domodedovo Airport said the air traffic controller's instructions take priority over the on-board anti-collision system when the two contradict.
``The air traffic controller gets the last word,'' said Sergei Rybanov of Bashkirian Airlines.
That is an international rule, said Rybanov and a spokeswoman for Domodedovo Airport, where the Russian flight originated.
But Herbert Schmell, spokesman for the national airline Swiss, said the cockpit warning system should have been obeyed.
``A TCAS system makes no sense if it is overruled, especially in a phase when there isn't much leeway anymore,'' Schmell said.
Georg Fongern, a spokesman for Germany's pilot association, agreed, saying the planes never should have been allowed to get so close that the warning systems kicked in.
``Never in the life of an aircraft should this system be activated, and if it has been activated there have to be a lot of mistakes and deficiencies beforehand,'' Fongern said.
Axel Raab, a spokesman for German air traffic control, told ZDF television the problem was that no international regulation tells pilots whether to follow the controller's order or the warning system.
``In most countries the rule is quite clear - pilots must follow the collision warning system,'' he added. ``But unfortunately that is not yet the case everywhere.''
Other experts said the planes would have had enough time to avoid each other had they both followed their cockpit warnings.
In another development, German air controllers said Monday they received an automatic radar warning that the planes were on a collision course and tried to warn the Zurich tower about two minutes before impact.
But when they called, the only available line was repeatedly busy.
German investigators said last week the Zurich control center's telephone system was undergoing maintenance at the time and the lone controller on duty was using the reserve line to communicate with Friedrichshafen, Germany, controllers about another flight.
Zurich's collision-warning system also was out of service for maintenance.
Most of the wreckage has been recovered and now is at the Friedrichshafen airport for investigation. A Braunschweig laboratory is examining the flight data and cockpit voice recorders of both planes.
Russian President Vladimir Putin visited a cemetery Monday in Ufa, the capital of the Bashkortostan republic, during a memorial service for victims.
Putin told the Russian captain's widow that, according to his information, ``the Russian pilots were not to blame for the tragedy.''
``The Russian pilots were professionals of the highest class,'' the ITAR-Tass news agency quoted him as saying.
07/08/02 18:39 EDT