A plane crash in northwestern Iran on Wednesday involved the Tupolev Tu-154 airliner, a Russian-built workhorse which went into service in 1972.

Here are some details about the Tu-154 and its safety record:

* The Tu-154 is the standard airliner on Russian domestic routes and other states of the former Soviet Union and to a lesser extent in eastern Europe and Iran

* It seats up to 180 passengers with 3-4 crew

* It was Russia's answer to a pair of Western planes from the 1960s also configured with three engines at the rear -- the Boeing 727 and Britain's Hawker Siddeley Trident

* Russian airline safety hit rock bottom during the economic chaos of the early 1990s when there were at least 10 fatal crashes involving the Tu-154

* Two of the worst crashes in the last 30 years involved the Tu-154 in the 1980s - one in 1984 when an Aeroflot Tu-154 collided with two airport service vehicles while landing at Omsk, Russia, killing around 174 people, and one in July 1985 when an Aeroflot Tu-154 crashed in Uzbekistan killing 200

* Wednesday marked the third deadly crash of a Tu-154 in Iran since 2002 and the deadliest crash in the Islamic Republic since 2003

* The Tu-154 first flew in 1968, was delivered to Aeroflot in early 1971 and entered regular service in February 1972. There were major upgrades in the 1980s and 1990s to improve the wings, engines and avionics

* More than 900 of the planes have been produced including freighter versions and about 250 remain in service

Sources: Reuters, www.aerotransport.org, www.tupolev.ru, www.flightlevel350.com, www.airliners.net

(Writing by David Cutler, London Editorial Reference Unit; Editing by Jason Neely)