Swiss ATCs cut burden after crash

Relatives left tributes in the wreckage when they visited the site

ZURICH, Switzerland -- Stress caused to staff following last week's mid-air plane disaster has forced the Swiss air traffic control organisation at the centre of the crash investigation to reduce its capacity by 20 percent.

Skyguide spokesman Felix Hitz said the measure, which comes at the start of the busy summer holiday season in Europe, would last a few days.

"They are used to stress in their work but this is another kind of stress," he said.

Some flights over the area will be rerouted by Eurocontrol in Brussels.

Seventy-one people -- many of them children -- died on Monday over southern Germany when a Russian Tupelov-154 passenger plane collided with a Boeing 757 cargo service.

CNN NewsPass VIDEO Investigation centres on Swiss air traffic control, says CNN's Stephanie Halasz (July 4) Play video   RESOURCES Gallery: Relatives' grief  Gallery: Jets collide over Germany    MORE STORIES • Trauma for relatives  • Terror at 36,000 feet  • Children's holiday party on doomed plane  • Planes fell in 'ball of flames'  • Crash comes after air traffic change  • Midair crash: Nightmare scenario    EXTRA INFORMATION • Map: Crash area  • Details of the jets  • Major Russian crashes  • Recent plane crashes

Skyguide's move came as investigators began analysing flight recorders from the planes.

"They are working today in analysing the voice and data recorders from the two airplanes," an official at Germany's BFU accident investigation agency told Reuters.

BFU said two German and one Russian expert were examining the recorders.

The crash happened under Skyguide's watch in the Swiss-German border region.

The reduction in Skyguide operations will cause delays to flights in and out of Zurich.

Alain Rossier, chief executive of Skyguide, admitted on Saturday his organisation may have made errors.

Investigators are analysing flight recorders from the two aircraft to try to determine the cause of the crash.

The German BFU investigation bureau said in a report that the Skyguide controllers' main telephone line was down while the anti-collision alert system was switched off for maintenance.

A single controller was overseeing five planes in the area while a colleague was having a break.

The controller, who has been receiving counselling since the disaster, issued a warning to the Russian plane only 44 seconds before the crash. The warning time should be 90 seconds.

In addition, a collision warning system had been taken out of service for repairs 35 minutes earlier.

Rossier told Swiss Radio there were three key areas to be investigated -- the reactions of the sky controller's reactions, the pilots' reactions and the planes' techinical systems.

"Only then can one say whether it is just a breakdown by us or a breakdown by others as well," Rossier said.

Swiss officials have opened a criminal investigation into possible negligent homicide.

Crash investigators comb the wreckage

Rossier said in a statement on the Skyguide website on Friday his organisation would not duck hard questions.

"We will do our utmost the find the reasons for this tragedy. We are awaiting the results of the investigating authorities and we will not shirk our responsibility," he said.

"All of Skyguide is aghast at the tragic accident in Ueberlingen. Deeply dismayed, we mourn along with the relatives of the victims."

Meanwhile, poor weather hampered the recovery operation at the crash scene on Saturday as workers tried to gather wreckage scattered outside the town of Ueberlingen on the German side of Lake Constance.