KIEV • Yesterday's plane crash in Iran that killed 176 people was the first fatal incident involving Ukraine International Airlines (UIA), and the Boeing 737-800 - one of the best in its fleet - was flown by experienced pilots, airline officials said.

It was not immediately clear what caused the crash, which occurred hours after an Iranian missile attack on United States-led forces in Iraq.

Ukraine set up a commission to investigate the crash, while UIA said the aircraft had been in good working order and that it was doing all it could to establish what happened.

Founded in 1992 after the collapse of the Soviet Union, UIA operates out of Kiev's Boryspil airport.

Planes operated by the loss-making, privately held UIA have suffered technical problems in flight but have never crashed before.

UIA officials told a news conference yesterday that the Boeing 737-800 involved in the fatal crash was one of the best planes they had and that its pilots were very experienced.

Airline officials said there was no sign that anything was wrong before the plane took off from Teheran's Imam Khomeini airport and that it had last been routinely serviced on Monday.

The plane, which the company said had mostly been carrying passengers planning to transit via Ukraine to destinations in Europe, was manufactured in 2016 and was acquired directly from Boeing, officials said.

On its website, UIA says it had been awarded the IOSA - the Iata (International Air Transport Association) Operational Safety Audit certificate - meaning its operational and safety standards are fully in line with international requirements.

The airline, which operates domestic and international flights, has a fleet of 42 planes made up of various Boeing aircraft, including 737-800s and 737-900s, says its website. UIA also operates Embraer aircraft.

Financial problems forced the airline to scale back its route network last year.

UIA is in the process of trying to modernise its fleet and has ordered three Boeing 737 Max aircraft, which it has not yet taken delivery of due to continuing safety concerns over the Max project.

According to The Guardian, the 737-800 belongs to the same family as, but is different from, the 737 Max 8 aircraft.

The 737 Max 8 has been grounded since last March after two fatal crashes occurred within six months in Indonesia and Ethiopia. The 737-800 operates with a different software system from the one implicated in the Max 8 crashes.

Several 737-800 aircraft have been involved in deadly accidents, The Guardian reported. In March 2016, a Flydubai 737-800 from Dubai crashed while trying to land at Rostov-on-Don airport in Russia, killing 62 on board.

Another 737-800 flight from Dubai, operated by Air India Express, crashed in May 2010 while trying to land in Mangalore, India, killing over 150 on board.

REUTERS