JERUSALEM (AP) — President Donald Trump said Thursday that Iran may be linked to the FlyDubai copilot who tried to crash an Israel-bound plane as investigators worked to determine why the copilot stabbed the flight's captain, causing the jetliner to plummet before others on board landed it in Saudi Arabia.

Trump was asked by reporters at the White House whether he had been briefed about any links between the pilot behind the attack and Tehran. He said, “We’re working on it right now.”

“I would say the answer, based on what I’m hearing, is yes, but we’re working on it right now,” Trump said. He did not elaborate why he thinks Iran might be involved.

Asked if the U.S. would retaliate against Tehran if it was behind the attack, Trump said, “Oh they’ll be hit, very hard, don’t worry.”

“You just ask them,” he added. “They know what happened. They’ll be hit very hard.”

His remarks come as diplomatic efforts to end the war appear to have stalled.

Iranian officials indicated Wednesday they received an official U.S. response to Tehran’s latest proposal to end the seven-month war, which Trump had publicly rejected just days earlier. The officials did not say what the response contained and whether it was a rejection.

Trump said in a Time magazine interview published Thursday that he will not accept proposals from Iran that “he wouldn’t have approved a year ago,” and left open the possibility of resuming bombing after the Nov. 3 election.

Despite Trump’s public rebuff, mediators have continued working with Iran and the U.S. to try to broker a deal to end the fighting and open the Strait of Hormuz, according to officials who were not authorized to comment publicly and spoke on condition of anonymity.

Passengers got into cockpit to take control of jet

Passengers on the FlyDubai plane — which was carrying 182 people, mostly Israelis, from the United Arab Emirates to Tel Aviv — have described how the bloodied Indian captain managed to open the cockpit door to let them in before they grappled with the copilot and stabilized a descent so sharp that the plane’s rudder was torn away.

“We felt helpless, suspended in midair, and I didn’t know who to turn to. But it was all instinct to survive,” Asaf Rajuan, who was among those who intervened, said in a statement shared by Israel’s presidency.

A regional official briefed on the investigation said the suspect, an Omani citizen, was under arrest and confirmed that Saudi authorities were working with countries, including Israel, to try to determine a motive. He said the UAE, the United States and Oman also were involved. Saudi Arabia said he had been handed over to the UAE.

“All possible scenarios, from terrorism to mental disorders, are being looked into. Nothing is ruled out for now,” said the official, speaking on condition of anonymity because they were not authorized to discuss an ongoing probe.

Israeli Prime Minister Benjamin Netanyahu, without giving details, claimed the attacker underwent Islamist indoctrination. Asked who helped radicalize him, the prime minister told Fox News channel’s “Fox and Friends" he did not know.

When asked by The Associated Press how the prime minister knew the copilot underwent indoctrination, Netanyahu’s office said it would not comment.

Netanyahu told Fox that the suspect apparently got through a loophole in Israeli aviation rules that normally bar pilots from flying to Israel if they are from countries that do not have diplomatic relations with Israel, which Oman does not.

The copilot has not been publicly identified. Video shot inside the plane by Dr. Shota Musayev, a dentist who treated the captain, shows the copilot on his knees, with his hands tied behind his back.

Capt. Smit Machchhar, widely praised as one of the heroes of the flight, was recovering in the Emirati capital of Abu Dhabi, the Indian government said Thursday.

It was not clear what the copilot used as a weapon.

Israeli investigators will join the interrogation of the copilot

Israeli intelligence and security officials were in Saudi Arabia to help investigate the copilot, according to another regional official who spoke on condition of anonymity because they were not authorized to speak to the media.

Israel has requested that the copilot be sent to Israel for the investigation, though it was unclear if that request would be granted, the official said.

Saudi Arabia does not have formal diplomatic ties with Israel, but the countries have long cooperated on security and intelligence matters through alternative channels.

The UAE government said its own investigation team had begun looking into the attack and “whether it was linked to any terrorist purpose,” noting that Emirati authorities have jurisdiction because the plane is registered there and UAE law applies to crimes committed on board.

Asked if there is any indication of Iranian involvement, Netanyahu told Fox News “it’s too early to say.”

Netanyahu earlier said he also spoke with the UAE’s president, Sheikh Mohamed bin Zayed Al Nahyan, who agreed that Israel would join the interrogation of the suspect.

On Wednesday, Trump told reporters at the White House that he and Netanyahu discussed the incident “at length” by phone, and it seemed as though the copilot “was perhaps a terrorist or perhaps a whack job.”

Oman's government has not commented.

Israel says it received no specific warning of an attack

Netanyahu had warned in recent days of heightened security threats, though he told CNN that Israel had received no specific warning. The country is a week away from the anniversary of the Hamas-led Oct. 7, 2023, attack on Israel, which has triggered the war in Gaza — and weeks away from an election.

The Israeli Foreign Ministry said most of the people on board were from Israel, along with others from India and the UAE. The U.S. State Department said four passengers had American citizenship.

FlyDubai has said its flights to and from Israel would be suspended. Netanyahu told CBS that Israel plans to fly home anyone stranded in Dubai as a result.

Someone in cockpit sent out discreet distress codes

Someone in the cockpit sent out two four-digit codes to discreetly signal distress while the plane flew erratically near the Jordanian border with Saudi Arabia, according to Flightradar24.com. The first code was “7700,” the universal “squawk” signal for an emergency, then “7500,” which indicates unlawful interference, including a possible hijacking.

The codes are used by pilots when speaking over the radio may not be possible or wise.

FlyDubai said Wednesday that the jet was secured by on-duty crew members “who diverted and landed the aircraft safely.” A regional official said the crew members were pilots in training. The official spoke on condition of anonymity because they were not authorized to speak to the media.

In the chaos that began about two and a half hours after takeoff, the Boeing 737 Max 8 descended from 33,000 feet to 17,000 feet (around 10,000 meters to 5,100 meters) in about a minute, before making an erratic circle close to the Jordanian border and landing in Tabuk, according to Flightradar24.

The head of the New Zealand flight school where the Indian captain trained, Philip Kean, called it “miraculous" that the aircraft, which was never designed for that sort of dive, did not break up completely.

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Magdy reported from Cairo. Price reported from Washington. Associated Press writers Josef Federman in Jerusalem and Laurie Kellman in London contributed to this report.