US President Donald Trump warned on Thursday that Iran will be “hit very hard” if it is found to be linked to a pilot’s attack on a flydubai flight to Israel.

The dramatic events a day earlier saw passengers help stop the plane from crashing, making an emergency landing in Saudi Arabia before the flight’s mostly Israeli passengers were flown home to a hero’s welcome.

Trump’s warning came as the United Arab Emirates opened an investigation into whether the incident was linked to terrorism, and Israeli Prime Minister Benjamin Netanyahu said the suspect had undergone “Islamist radical indoctrination”.

“I would say the answer, based on what I’m hearing, is yes, but we’re working on it right now,” Trump told reporters Thursday when asked at the White House whether Iran was involved in what happened on the flight from Dubai to Tel Aviv.

On whether the United States would retaliate against Iran if it was found responsible, Trump replied: “Oh, they’ll be hit very hard, don’t worry.”

Trump’s threat coincided with a wider US military buildup in the region.

Axios reported that Washington had recently deployed additional Patriot missile batteries to Saudi Arabia and Qatar to help protect key energy facilities from possible Iranian retaliation.

The US news outlet also reported that the USS Theodore Roosevelt aircraft carrier and its strike group were heading to the Middle East, where they could join two other US carrier strike groups already in the region.

As speculation swirled about a possible motive, the UAE and Saudi Arabia began to piece together the events in the cabin.

Saudi Arabia said the co-pilot was transferred to the UAE on Thursday accompanied by an “Emirati security team”, adding that its initial investigation showed he had attacked the aircraft’s captain.

The alleged assault triggered a struggle for control of the aircraft before an emergency landing in Saudi Arabia. Passengers were later flown to Israel on a replacement flight.

“We know that he underwent Islamist radical indoctrination,” Netanyahu told the “Fox & Friends” TV show, without elaborating.

“The attacker, he calls out to the aircrew, ‘Kill me, kill me’,” Netanyahu said, adding it was “clear he was suicidal”.

His comments came after the UAE chief prosecutor said investigators would explore whether there had been “terrorist activity or intent”.

Netanyahu said the UAE would lead the investigation while Israel would participate.

He identified the co-pilot as an Omani national and said Israel would check how he had been cleared to work on flights to the country.

“We have constraints that say that you can’t have pilots from countries that don’t have diplomatic relations with Israel. Obviously he was able to go through that,” Netanyahu told Fox News.

Netanyahu had earlier credited captain Smit Machchhar, an Indian national, and passengers with averting catastrophe after the co-pilot allegedly stabbed him and tried to crash the plane.

Passengers described rushing the cockpit and a fight for control after the plane suddenly plummeted, losing around 17,000 feet of altitude in the span of a minute, according to the Flightradar24 website.

Israeli officials have called the incident “an attempted terrorist attack”, although Netanyahu in an earlier interview with CBS News had not ruled out the possibility that mental health was to blame.

“During the flight, as they approached the country, one of the pilots stabbed the other pilot, and apparently tried to crash the plane with everyone on board,” Netanyahu had said in a video message.

Netanyahu later praised Machchhar “for his extraordinary bravery”.

The Indian ambassador to the UAE visited the wounded captain, with the embassy saying he was in “good health and recovering well”.

Indian Prime Minister Narendra Modi described him as a “HERO”, saying his actions had helped save lives.

Passenger Miryam Shira Ohayon said the aircraft was “pretty much out of control” as the incident unfolded over Jordan.

“The co-pilot tried to murder the pilot and basically carry out a suicide attack on the plane,” she told reporters.

“It was really on the way to crashing, and it was simply the resourcefulness of many people who took control of the co-pilot and neutralised him.”

Flydubai said another “on-duty Flydubai crew travelling on the flight… landed the aircraft safely” and announced it was suspending flights to Israel while the investigation continued.

Israeli President Isaac Herzog said he would honour five Israelis who helped overpower the co-pilot and prevent the plane from crashing.

AFP