Firemen work at the crash site of the Russian Tupolev Tu-154 plane, east of Kiev, August 22,2006

Russia observed a day of mourning Thursday for the passengers and crew of a Russian airliner that crashed in eastern Ukraine Tuesday, killing everyone on board.

Russian President Vladimir Putin ordered flags to be flown at half-staff nationwide. He advised broadcasters to cancel entertainment programs, and recommended cultural performances also be canceled.

Memorials are being held in several Russian cities.

Pulkovo Airlines says 170 passengers and crew were killed when its TU-154 jet crashed during stormy weather. But, Russian officials say 171 bodies have been recovered from the crash site in the marshy, eastern Ukraine countryside near the village of Sukha Balka. It was headed to St. Petersburg from Anapa, a Russian Black Sea resort.

Investigators are analyzing the plane's flight data recorders to determine what caused the crash. Russian and Ukrainian officials say the jet may have been hit by lightning or a sudden wind change.