sian doctor famous for her work in war zones.
Russian President Vladimir Putin went on television to declare Monday a nationwide day of mourning.
“We will conduct a thorough investigation into the reasons and will do everything to support the victims’ families,” Putin said.
The Black Sea search area — which covered over about 4 square miles — was made more difficult by underwater currents that car- ried debris and body fragments into the open sea. Sokolov said the plane’s flight recorders did not have radio beacons, so locating them on the seabed was going to be challenging.
The Tu-154 is a Sovietbuilt three-engine airliner designed in the late 1960s. More than 1,000 have been built, and they have been used extensively in Russia and worldwide. The plane that crashed Sunday was built in 1983, and underwent factory check-ups and maintenance in 2014 and this year, according to the Defense Ministry.
Magomed Tolboyev, a decorated Russian test pilot, said it was clear that all on board had died in the crash.
“There is no chance to survive in such situation,” he said, according to the Interfax news agency.
Before Sokolov spoke to reporters in Sochi, senior Russian lawmakers had ruled out a terror attack, arguing that the military plane was under reliable protection.
Security is particularly tight in Sochi, the Black Sea city that hosted the 2014 Winter Games and is regularly visited by Putin, who often receives foreign leaders at his residence there.
But some experts said the crew’s failure to report a malfunction pointed at a possible terror attack.
“Possible malfunctions ... certainly wouldn’t have prevented the crew from reporting them,” Vitaly Andreyev, a former senior Russian air traffic controller, told RIA Novosti.