BERLIN ÷ Both pilots of the planes that slammed into each other over Germany notified Swiss air traffic control less than a minute before impact that they were descending, investigators said.

The German investigation into the crash that killed 71 people last week sharpened its focus on the apparently conflicting instructions to the Russian charter planeās pilot from controllers on the ground and the on-board collision warning system. Investigators are ćlooking to clarify what the real legal situation isä in such a case, said spokesman Odo Zboralski.

Analysis of the cockpit voice recorders shows that the Bashkirian Airlines pilot acknowledged the controllerās order to descend about 30 seconds before the collision, but he did not mention an order to climb that he had received from his cockpit warning system, Zboralski said.

Some 15 seconds before, the pilot of the other aircraft, a DHL International cargo jet, told ground control over his radio that he was following a cockpit computer warning to descend.

ćBut there was no acknowledgment from the ground station to (the DHL plane), itās just on the tape and we are not so sure if the controller really got that message,ä Zboralski said.

Swiss air traffic controllers had taken over the planes as they approached one another over the German-Swiss border just before midnight July 1. The crash killed 69 people on the Russian plane, including 45 school students heading for a Spanish beach vacation, and the two DHL pilots.