A Russian airliner crash killed four people Saturday when a plane slid off an airport runway outside Moscow and crashed onto a highway.

Initial reports indicated 12 crew members were aboard the Red Wings Airlines flight, but that number was later revised to eight. The four survivors were all injured when the plane overshot the runway after traveling to Russia from the Czech Republic, according to CNN.

Witnesses told Reuters the Tupolev Tu-204 jet's cockpit broke completely free of the rest of the plane while the tail of the ship was engulfed in flames. They said they saw one man being thrown from the plane before it jolted onto the highway not far from the edge of the runway. “We could not get the pilot out of the cockpit, but we saw a lot of blood,” one person on the scene said.

“We saw how the plane skidded off the runway ... The nose, where business class is, broke off, and a man fell out," said a witness identifying himself as Alexei. "We helped him get into a minibus to take him to the hospital."

Airport representative Yelena Krylova said, “The plane split into three pieces.”

An early investigation pointed to pilot error as a possible cause of the crash, but the safety of Russian aviation has been suspect for a long time. President Vladimir Putin has publicly said the industry must improve its protection of passengers.

The Tu-204 airliner has been in production since the mid-1990s, and before Saturday it had never been involved in a fatal crash, Reuters reported. The plane has room for 210 passengers.