Boeing 737

US, Canadian and UK officials claim that a Ukrainian Boeing 737 commercial aircraft that crashed shortly after takeoff from Tehran was mistakenly downed by a Russian-made surface-to-air missile system fired by Iran. However, there is still an investigation pending and Iran has responded by calling the theory a "big lie."

CHICAGO — The fatal crash of Ethiopian Airlines Flight 302, just months after the Lion Air Flight 610 crash in Indonesia, has led to governments and airlines around the world grounding their Boeing 737 Max 8 aircraft amid concerns that, after two crashes killing 346 people, the model is unsafe to fly. Airlines are attempting to cancel their orders of the aircraft, citing public-safety fears.