Rumours and speculation are swirling about the Ukraine International Airlines jet which crashed in Tehran, killing all 180 passengers and crew on board within seconds of takeoff.

Iran’s semi-official Fars news agency immediately attributed the Boeing 737-800’s fiery plunge into a field outside the country’s biggest city to “technical problems” – an explanation that stunned aviation experts who noted the aircraft’s black boxes had not yet been recovered.

Iran officials confirmed the flight recorders were found late on Wednesday night (AEST) but would not say if their contents would be released.

Eyebrows also were raised by Ukraine’s response, which saw officials initially endorse the mechanical-failure diagnosis, only to back away from it within hours.

They noted that the plane, one of Boeing’s most reliable models, had been serviced within the past week and was only three years old.

Adding to to the intrigue were unconfirmed reports that panels of the shattered wreckage appeared to have been penetrated by projectiles.

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Adding to what promises to be an acrimonious investigation is the fact that, under international aviation accords, manufacturer’s representatives are entitled to take part.

With Iran and the US exchanging insults and missiles, Seattle-based Boeing’s involvement has to be considered dubious in the extreme.

Qantas immediately reacted to the news by re-routing all flights away from Iranian airspace, adding an extra 60 minutes to the London-Sydney flight time.

Pir Hossein Kulivand, head of Iran’s emergency services, made the confirmation, saying rescuers were trying to collect the dead.

More than 60 Canadians perished in the disaster, 11 Ukrainian nationals and 82 Iranians.

An investigation team was at the site of the crash in south-western outskirts of Tehran, civil aviation spokesman Reza Jafarzadeh told the Associated Press.

Iranian news agency ISNA shared a video purporting to be of the crash.

The footage appeared to show the airliner impacting with the ground in a massive ball of flames.

Flight data from the airport showed a Ukrainian 737-800 flown by Ukraine International Airlines took off Wednesday morning, then stopped sending data almost immediately afterward, according to website FlightRadar24.

Head bowed, a recovery team member surveys the passengers’ bagged bodies.passengers. Photo: AP

The crash came hours after Iran launched a ballistic missile attack targeting two bases in Iraq housing US forces in retaliation for the killing of Revolutionary Guard General Qassem Soleimani.

The Boeing 737-800 is a common single-aisle, twin-engine aircraft used for short to medium-range flights.

First introduced in the late 1990s, thousands of the planes are in use by airlines around the world.

It is an older model than the Boeing 737 MAX, which has been grounded for nearly 10 months following two deadly crashes.

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.

Chicago-based Boeing Co. was “aware of the media reports out of Iran and we are gathering more information,” spokesman Michael Friedman told The Associated Press.

Boeing, like other airline manufacturers, typically assists in crash investigations. However, that effort in this case could be affected by the US sanctions campaign in place on Iran since President Donald Trump unilaterally withdrew from Tehran’s nuclear deal with world powers in May 2018.

Both Airbus and Boeing had been in line to sell billions of dollars of aircraft to Iran over the deal, which saw Tehran limit its enrichment of uranium in exchange for the lifting of economic sanctions. But Trump’s decision halted the sales.

Under decades of international sanctions, Iran’s commercial passenger aircraft fleet has aged, with air accidents occurring regularly for domestic carriers in recent years, resulting in hundreds of casualties.

-with AAP