Security has been tightened at Russian airports after a jetliner crashed 125 miles south of Moscow and another apparently went down at nearly the same time 500 miles farther south.
The second plane disappeared and no wreckage has been found. But the Interfax news agency reports searchers have spotted a fire in the area.
No word yet on survivors. Eighty-eight people are believed to have been aboard the two planes.
President Vladimir Putin has ordered the nation's top intelligence agency to investigate and authorities are not ruling out terrorism.
A presidential election is set for Sunday in Chechnya, where separatist rebels have been blamed for terror attacks that have killed hundreds of people.
Witnesses report seeing an explosion before the first plane crashed. Rescuers have found the tail of that plane.
Both flights originated in Moscow.