A Ukrainian passenger plane was carrying dozens of Canadians — some believed to be university students — when it crashed minutes after takeoff from Tehran's main airport The Ukraine International Airlines Boeing 737-800, was en route to Kyiv when it went down in a field Authorities say all 176 on board were killed — including 63 Canadians, 82 Iranians, 11 Ukrainian passengers and crew, 10 Swedes, four Afghans, three Germans and three Britons The crash came hours after Iran launched a ballistic missile attack on Iraqi bases housing U.S. soldiers for a drone attack on a top Iranian general on January 2nd Both Ukrainian and Iranian officials said they suspected a mechanical issue brought down the Boeing 737-800 aircraft Ukrainian authorities later walked their comments back, saying nothing had been ruled out The Boeing 737-800 is a very common single-aisle, twin-engine jetliner used for short to medium-range flights Thousands of the planes are used by airlines around the world Introduced in the late 1990s, it is an older model than the Boeing 737 MAX, which has been grounded for nearly 10 months following two deadly crashes Boeing built the aircraft that crashed Wednesday in 2016 and it last underwent routine maintenance on Monday, Ukraine International Airlines said A number of 737-800 aircraft have been involved in deadly accidents over the years In March 2016, a FlyDubai 737-800 from Dubai crashed while trying to land at Rostov-on-Don airport in Russia, killing 62 onboard Another 737-800 flight from Dubai, operated by Air India Express, crashed in May 2010 while trying to land in Mangalore, India, killing more than 150 onboard