Ukraine International Airlines (UIA) flight PS752 was attempting to return to Tehran’s Imam Khomeini International Airport when it crashed Jan. 8, killing all 176 people on board, Iran’s civil aviation authority said in a statement on its website. 

The authority added that pilots did not send any radio message for help. 

The Boeing 737-800’s flight recorders, aka black boxes, were damaged when the aircraft crashed but have been recovered, the authority said. Ukrainian accident investigators confirmed they had arrived in Tehran and would take part in analyzing data.  

The aircraft, registered UR-PSR, departed at 6:10 a.m. Tehran time Jan. 8 on a regularly scheduled, 4 hr., 15-min flight to Kyiv Boryspil International Airport (KBP). The 737 disappeared from radar less than 3 min. later and crashed, creating a debris field about 9 mi. north of IKA in a suburb of Tehran, several miles east of its last transponder position. 

“The black boxes containing the flight information recorder (FDR) and the cockpit voice recorder (CVR) were found by search and rescue agents and are in the possession of the accident investigation team,” Iran’s Civil Aviation Organization said in a statement on its website, citing its head, Ali Abedzadeh. “Both devices were damaged by accident and fire. There is memory in both devices, but physical damage is visible on them.”

Amid rising tensions in the region, the crash happened shortly after Iran launched missile attacks from inside the country on U.S.-related targets in Iraq. The FAA subsequently banned U.S. carriers from flying over Iran, Iraq, the Persian Gulf and the Gulf of Oman, and other airlines from around the world soon began re-routing traffic around the area, modifying their schedules and canceling some flights. 

Documentation and evidence of the accident site had been reviewed and the remaining parts of the aircraft collected and transported to a safe location, the statement continued. 

Abedzadeh was quoted as saying: “The aircraft first rises to an altitude of 8,000 feet and then the aircraft’s information is removed from the radar screen and the aircraft collides with the ground and collapses. No radio messages were received by the pilot regarding unusual circumstances. According to eyewitness reports (people on the ground and high altitude flight crew who observed and reported the incident), a fire was observed in the aircraft and increased in range and after the aircraft hit the ground, an explosion occurred.”

He also said that the aircraft, which initially headed westward, was on its way back to the airport at the time of the crash, adding: “The accident site documentation shows that the plane’s first collision with the ground was in an amusement park area. After that initial collision, other collisions were observed along its trajectory and the body of the plane collapsed and spread along the trajectory.” 

The 737-800 aircraft had been delivered new to the airline in July 2016 and UIA said it underwent scheduled maintenance Jan. 6. In a Jan. 9 update on its website, Ukraine’s National Bureau of Investigation of Air Accidents (NBAAI) confirmed a group of its advisors and experts had arrived in Iran and that Ukrainian representatives would participate in the read-out, processing and analysis of flight and voice data obtained from the black boxes. 

“Investigators would have to collect as much information as possible on the accident site, assess the wreckage in order to control the objectiveness and impartiality of the investigation process,” the NBAAI said. 

Ukrainian president Volodymyr Zelensky said in a statement posted on his website Jan. 9 that 45 specialists from Ukraine had arrived in Iran as part of the search and rescue team, including officials of the State Aviation Service, the NBAAI and UIA representatives. They were set to visit the crash site and were expected to be involved in all the work of the commission set up by Iran’s civil aviation authority, including decoding the black box data, he said. 

“Undoubtedly, the priority for Ukraine is to identify the causes of the plane crash. We will surely find out the truth. For this purpose, a thorough and independent investigation will be conducted in accordance with international law,” Zelensky said. “Today, I will hold a phone conversation with the president of Iran to step up cooperation with the Ukrainian side to establish the truth. I also call on the international community, in particular Canada, to join the investigation into the circumstances of the Ukrainian Boeing 737 crash.”