Reports of the strike came as survivors told how they escaped the Aeroflot jet which burst into flames on landing at Sheremetyevo airport on Sunday.
Forty-one of the 78 people on board were killed in the accident.
Investigators probing the cause of the crash have made no official comment on the claims it was hit by lightning.
Modern aircraft are built to withstand lightning strikes, and Russia's national carrier has said only that the plane returned to the airport for "technical reasons".
However passengers said the plane, which was heading for the northern Russian city of Murmansk, was struck just after take-off.
Some of the five crew members also said lightning appeared to be responsible for a loss of communication with air traffic control.