What might have caused the helicopter crash that killed Iran's president

The crash that killed Iranian President Ebrahim Raisi and several other top officials on Sunday was the latest high-profile deadly helicopter accident in recent years.

For most people, the death of retired NBA star Kobe Bryant, his 13-year-old daughter and seven others in a helicopter crash in California four years ago comes to mind. But in 2018, Thai businessman Vichai Srivaddhanaprabha, who owned the Leicester City soccer club, died along with four others in a helicopter crash. The previous year, Troy Gentry, then part of country music act Montgomery Gentry, was also killed in a crash in New Jersey.

An investigation of the crash that killed Bryant and the others aboard a Sikorsky S-76B concluded that the pilot became disoriented as the chopper flew into a cloud bank, thinking he was climbing when in fact he was plunging into a hillside. Pilot error was also blamed in the crash that killed Gentry, while an investigation of the crash involving Vichai concluded that the Leonardo AW169 helicopter was brought down by a failure of its rear rotor mechanism.

It's impossible to say with certainty what may have caused the crash in Iran on Sunday that killed Raisi, Iranian Foreign Minister Hossein Amir-Abdollahian and the others. But one or more of the factors below may have played a part.

Could bad weather have been a factor in the fatal crash?

Early reports of the crash in Iran suggest that the helicopter was flying in a "foggy, mountainous region of the country's northwest," according to The Associated Press.

Poor weather conditions are a leading cause of helicopter, or rotor aircraft, crashes. According to an analysis presented at a 2021 forum of the American Institute of Aeronautics and Astronautics, in 28% of all fatal helicopter crashes, weather was a factor.

"Wind was involved in most incidents but more rarely involved in fatalities. Bad visibility conditions due to a combination of low illumination and clouds were responsible for most fatal weather-related accidents," the analysis says in its synopsis.

It notes that helicopters "typically operate at lower altitudes than fixed-wing aircraft and can take-off and land away from airports. Thus, helicopter pilots have decreased access to weather information due to connectivity issues or sparsity of weather coverage in those areas and at those altitudes."

In February, five Marines were killed when their CH-53E Super Stallion — the largest helicopter operated by the U.S. military — crashed into mountains outside San Diego during a storm.

Helicopters are more dangerous than planes

While directly comparing the safety records of different modes of transportation is fraught with difficulties, an analysis conducted by the travel site The Points Guy in 2019 suggests that airline flights are considerably safer than "non-scheduled helicopter flights." However, those helicopter flights still scored much better for safety than driving or riding in a car or SUV or even "general aviation," such as flights in private planes.

Because of automation, most airplanes are forgiving of a pilot's momentary distraction, but "helicopters require a lot of concentration," John Goglia, a former member of the National Transportation Safety Board, said earlier this year, speaking to PBS. "And so sometimes people will lose their focus, and [then] the consequences are severe."

The Iranian president's helicopter was an old aircraft

The helicopter that crashed in Iran was a Bell 212, a twin-engine civilian version of the venerable "Huey" UH-1 that became ubiquitous during the Vietnam War in the 1960s and '70s.

The Aviation Safety Network, which maintains a database of accidents for various aircraft, shows that the Bell 212 and its military equivalents have experienced about 30 accidents since 2017, eight of them causing fatalities.

The Bell 212 in Iran was probably one bought in the 1970s while the Shah was still in power, prior to the country's 1979 Islamic Revolution, according to The National, the state-run English-language daily in the United Arab Emirates.

U.S. sanctions have made spare parts hard to obtain

According to the same paper, after the Shah was overthrown, Iran continued to use many U.S.-made aircraft "but faced difficulty obtaining spare parts due to American sanctions."

Iran's semiofficial Mehr News Agency in March quoted the deputy of the scientific department of knowledge-based economy development, Javad Mashayekh, as saying that the country had finally become 100% self-sufficient in supplying airplane spare parts. It did not say anything specifically about parts for helicopters.

Mashayekh was reported by Mehr News Agency as saying that previously Iran had been "highly dependent" on foreign sources for such parts and that U.S. sanctions imposed on Iran's nuclear program "caused a challenge in this regard."

In a commentary published by the Gulf International Forum, journalist Kourosh Ziabari wrote that "Iran's aviation industry has been blighted by years of neglect, underinvestment, and grueling sanctions" and that "accidents are recurrent and air transportation safety standards have steadily fallen."

Mysterious crashes have claimed the lives of politicians and rivals alike

Nothing immediate suggests sabotage as a possibility in the case of the helicopter crash in Iran, but using an aviation "accident" as a way to eliminate a national leader or political rival has been suspected in the past.

Last August, Yevgeny Prigozhin, the head of Russia's Wagner mercenary group, who led an abortive coup against the Kremlin, was killed when the private jet he was in plummeted into a field outside Moscow. Many believe the destruction of the plane was ordered by Russian President Vladimir Putin.

In April 1994, Rwandan President Juvénal Habyarimana, a Hutu, was killed when the aircraft he was in was shot down by a missile — an incident that triggered the Rwandan genocide. An inquiry did not bring charges against alleged culprits.

And in 1988, Pakistani President Muhammad Zia-ul-Haq was killed when the C-130 transport plane he was aboard suddenly crashed shortly after taking off from an airport in Pakistan's eastern city of Bahawalpur. At the time, witnesses reported seeing the plane flying erratically and then nosing down.

An official Pakistani report later concluded that "in the absence of a technical reason, the only other possible cause of the accident is the occurrence of a criminal act or sabotage."