Iran plane crash: Everything we know about the Ukraine Boeing 737 crash

It is believed all 176 people died in the Ukraine International Airlines accident

Rescue workers in Iran are surveying the wreckage of a Boeing 737-800 jet which crashed shortly after take-off from Tehran. The Ukraine International Airlines (UIA) plane was believed to be carrying 176 passengers and nine crew. There are said to be no survivors.

The airline has said: "UIA expresses its deepest condolences to the families of the victims of the air crash and will do everything possible to support the relatives of the victims." It has set up a dedicated telephone number for relatives of passengers: +38 044 581 50 19.

What were the circumstances?

The plane used for flight PS752 had taken off about 20 minutes late from Boryspil airport, east of Kiev, on Tuesday evening, on its journey to the Iranian capital.

As normal the plane flew south to the Black Sea to avoid the airspace of Russian-occupied Crimea and Russia itself, before turning southeast to fly to Tehran.

It landed slightly ahead of schedule at Tehran’s Imam Khomeini airport, just before 1am. The usual scheduling is for the aircraft to remain on the ground for just over four hours. But for reasons that are not yet known, its departure was delayed by 57 minutes.

It appears that the aircraft experienced problems very shortly after take-off. it crashed around two minutes after take off. Footage posted on social media appears to show the aircraft on fire and flying erratically before it crashed in open country a few miles northwest of the airport.

What is known about the aircraft – and its safety record?

It was a Boeing 737-800, registration UR-PSR, which had been delivered new to UIA from the US planemaker in July 2016 – making it relatively young.

The aircraft was configured to hold 186 passengers in two classes. It was used across the airline's short- and mid-haul network, and had operated a Kiev-Gatwick-Kiev round-trip on Monday 6 January.

The 737-800 is the most popular of Boeing’s NG (“Next Generation”) series of the highly successful twin jet, along with the larger -900 and the smaller -600 and -700.

Relative to the numbers flying, the accident rate is not disproportionate.

It is the only type of aircraft used by Ryanair, which is the world’s safest airline in terms of passengers flown without a single fatal accident.

The most recent fatal accident involving the Boeing 737-800 took place on the Micronesian island of Chuuk in September 2018, when an Air Niugini flight landed in shallow water short of the runway. One passenger died.

In 2016 a FlyDubai 737-800 crashed beside the runway at Rostov-on-Don in Russia, with the loss of 62 lives.

What are the possible causes?

It is too early to draw any conclusions. As the crash happened shortly after take off, investigators will look at a range of possibilities that include a possible bird strike (as happened to US Airways flight 1549, also known as "the miracle on the Hudson" in 2009) or any other kind of "foreign object ingestion" into the engines.

They will also consider whether one of the two CFM56 engines suffered an uncontained failure, such as that which killed a Southwest Airlines passenger on a flight in 2018.

Any plane crash will also be analysed for the possible effects of weather, human interference or pilot error – though there were three highly experienced captains and a first officer on board.

In a similar plane crash in Kazakhstan in December 2019, most passengers survived. Why was this different?

The Bek Air accident in Almaty took place at a much lower speed, with the aircraft barely airborne before it crashed. The Tehran crash happened from a greater height and significant speed. The high energy made the crash unsurvivable.

Was this connected with the Boeing 737 Max crashes, which also happened shortly after take off?

At present that seems extremely unlikely. The Max is the successor to the 737-800. But the older jet does not have the “anti-stall software” known as MCAS, which was implicated in the losses of Lion Air and Ethiopian Airlines Boeing 737 Max crashes in which 346 people died.

What is known about the airline?

The arrival screen at Kiev Boryspil airport, showing the Tehran flight as 'cancelled'

UIA was created after the collapse of the Soviet Union and Ukraine’s independence, and is the national carrier. But it is struggling financially. One reason is that it cannot use Russian airspace and is excluded from Crimea, the Ukrainian territory currently occupied by Russia. This prohibition reduces its potential route network and extends many journey times.

It is also facing intense competition from budget airlines, in particular Wizz Air and Ryanair.

In response the airline’s business model changed three months ago to exploit the “hub-and-spoke” network. Many of the passengers on the doomed flight would be intending to change planes to destinations in western Europe, including London Gatwick.

How is aviation safety in Ukraine rated internationally?

The most recent audit by the International Civil Aviation Organisation, in 2017, found Ukraine to be below average for licensing, legislation, airworthiness, accident investigation and operations.

The biggest aviation disaster in recent history was the crash of Malaysia Airlines flight MH17 in July 2014 on a flight from Amsterdam to Kuala Lumpur. The Boeing 777 with 298 people onboard was shot down by a missile fired from rebel-held eastern Ukraine.