Iran faces a shortage of parts to maintain aircraft. Iran’s state media said the helicopter that crashed was a Bell 212 that Iran purchased in the early 2000s. Bell produced that model from 1968 until 1998.

Richard Aboulafia, an aerospace analyst and consultant, said Iran likely is tapping the black market for parts amid sanctions on the country. But he said Iran had access to an alternative in Russian helicopters.

“They are blaming sanctions and that’s correct, but there are no sanctions whatsoever on (Iran buying) Russian helicopters, and Russian helicopters are pretty good. They didn’t have to fly this guy around” in such an old machine, Aboulafia said. “They are blaming sanctions for their own incompetence. You could buy an MI-17 anytime. It’s what Vladimir Putin flies in.”

Aboulafia also questioned whether Iran has maintenance skills necessary for keeping older helicopters flying safely.

“There are a lot of parts available on the black market, especially for a 212 – that’s a very old machine,” he said. “Half-century-old helicopters, if immaculately maintained, are OK. But black-market parts and whatever local maintenance capabilities they’ve got – that’s not a good combination.”

President Raisi was seen as a protégé to Iran’s supreme leader Ayatollah Ali Khamenei and a potential successor for his position within the country’s Shiite theocracy. Under the Iranian constitution, if a president dies, the country’s first vice president – in this case, Mohammad Mokhber – would become president.

Khamenei has publicly assured Iranians that there would be “no disruption to the operations of the country” as a result of the crash.

Iran has spent decades supporting armed groups and militants in Lebanon, Syria, Iraq, Yemen and the Palestinian territories, allowing it to project power and potentially deter attacks from the United States or Israel, the sworn enemies of its 1979 Islamic Revolution.

Tensions have never been higher than they were last month, when Iran under Raisi and Supreme Leader Ayatollah Ali Khamenei launched hundreds of drones and ballistic missiles at Israel in response to an airstrike on an Iranian Consulate in Syria that killed two Iranian generals and five officers.

Israel, with the help of the United States, Britain, Jordan and others, intercepted nearly all the projectiles. In response, Israel apparently launched its own strike against an air defence radar system in the Iranian city of Isfahan, causing no casualties but sending an unmistakable message.

The ongoing war between Israel and Hamas has drawn in other Iranian allies, with each attack and counterattack threatening to set off a wider war.

It’s a combustible mix that could be ignited by unexpected events, such as Sunday’s deadly crash.

Meanwhile, after the news first broke of the search operation, countries including Russia, Iraq and Qatar made formal statements of concern about Raisi’s fate and offered to assist in the search.

Azerbaijani President Aliyev offered any support necessary. Relations between the two countries have been chilly due to Azerbaijan’s diplomatic relations with Israel, Iran’s regional arch-enemy.

Saudi Arabia, traditionally a rival of Iran although the two countries have recently made a rapprochement, said it stands by “Iran in these difficult circumstances.”

There was no immediate official reaction from Israel. Last month, following an Israeli strike on an Iranian consular building in Damascus that killed two Iranian generals, Tehran launched hundreds of missiles and drones at Israel. They were mostly shot down and tensions have apparently since subsided.

• An AP report