One passenger airliner has crashed in Russia and there are fears that another plane may also have gone down. More than 40 people were on board each airliner. President Vladimir Putin has ordered the country's top security service to investigate immediately.
Wreckage of one airliner has been sighted near a village in the Tula region about 180 kilometers south of Moscow, while the other was reported missing while on its way to the Black Sea resort city of Sochi further south.
Emergency officials say the confirmed crash was a Tupolev 134 aircraft carrying 34 passengers and eight crew which was flying to the city of Volgograd.
The other plane was a larger Tupolev 154 with 44 people on board, which air controllers reported missing near the city of Rostov-on-Don near the Black Sea.
The Tula region is on the flight path for planes heading south from Moscow toward southern Russia.
Rescue teams with the Emergency Situations Ministry have confirmed finding wreckage of the first plane in the Tula region, and that witnesses reported hearing an explosion just before the crash.
Officials in Moscow say both planes dropped off of radar screens within minutes of each other, and that they couldn't rule out the possibility of terrorism.
Bombings have occurred in recent years in Moscow and other cities, some in southern Russia near the breakaway region of Chechnya where Russian troops have been battling separatist rebels for most of the past decade.
However many planes in Russia are old and mechanical problems are common, although the country's overall safety record has improved in recent years.