Russian authorities investigating Tuesday's almost simultaneous airliner crashes that killed 89 people are focusing on two female passengers with Chechen sounding names - one on each flight.
Officials say the women purchased tickets at the last minute and are the only victims whose families did not step forward to claim the remains.
Several suicide attacks in Russia in recent years have been blamed on widows of Chechen separatist fighters.
An Islamic group calling itself the Islambouli Brigades claimed responsibility for the plane crashes, citing solidarity with Chechen rebels.
On Friday, investigators at one of the crash sites reported finding traces of a high explosive, hexogen, used in the 1999 apartment bombings in Moscow that Russia blamed on Chechen separatists.
The planes went down just days before Kremlin-sponsored elections in Chechnya Sunday.