Disaster was averted on Wednesday's Flydubai flight FZ1073 from Dubai to Tel Aviv after the wounded captain managed to unlock the cockpit door, allowing passengers to subdue the attacker.
A reserve crew that had been aboard landed the plane, which had more than 170 people on board, at Tabuk airport in Saudi Arabia.
"We know that he underwent Islamist radical indoctrination. That appears to be something we are gathering from his personal information," Israeli Prime Minister Benjamin Netanyahu said in an interview with Fox News.
Two Israeli security officials said Israel's initial assessment was that the co-pilot, identified by Israel as an Omani citizen, was likely acting alone although the investigation was still ongoing.
The flight plunged more than 14,000 feet in less than 30 seconds during the incident as it flew over Saudi Arabia on the journey from the United Arab Emirates to Israel, according to the flight-tracking website Flightradar24.
Netanyahu said it was clear that the co-pilot intended to crash the aircraft.
"It looks very likely that he was going to down the plane," Netanyahu said.
Coupled with "the Islamist tendencies, that radicalisation that are found in his background, I think that's ... a pretty good clue," he said, without elaborating.
"But again, I don't make final conclusions yet. But that's the indications we have now," he added.
The United Arab Emirates has started investigations seeking to establish the circumstances and motives and determine "whether the incident was linked to any terrorist activity or purpose, or involved prior planning or direction," the UAE state news agency reported on Thursday.
Israeli envoy to the UAE Yossi Shelley told Reuters it was too early to draw conclusions and no motive had been determined.
Another Israeli official said Israel was not receiving all the information it sought from Saudi authorities and that the Israeli intelligence services Mossad and Shin Bet were investigating the incident as well.
Netanyahu identified the attacker as an Omani citizen.
Omani authorities have not commented.
"We have constraints that say you can't have pilots from countries that don't have diplomatic relations with Israel. So obviously he was able to go through that," Netanyahu told Fox.
In a separate interview with Fox News, Netanyahu said the attacker was being investigated in Saudi Arabia and he believed that he would be taken to the UAE.
Israeli Defence Minister Israel Katz said on Wednesday that Israel's preliminary information indicated that the co-pilot aimed to crash the plane, describing him as a terrorist, although Netanyahu only described it as "a serious security incident".
The incident heightened security fears in Israel weeks before Israelis vote in the first election since the Hamas-led attacks on October 7, 2023, with Israel's security figuring prominently in the campaigning.
Netanyahu and Indian Prime Minister Narendra Modi have hailed the flight FZ1073 captain and Indian citizen Smit Machchhar as a hero.
The pilot was recovering well, the Indian embassy in the UAE said on X.
Israel has also lauded passengers who subdued the attacker.
Yaniv Hayun, one of the men who incapacitated the attacker, described running to the cockpit as the plane nosedived.
"We pulled the assailant out, I pulled him out. After I pulled him out we took control of the plane, I pulled up the yoke (steering control of the plane), I straightened the plane out a bit," he said, talking to reporters upon his return to Israel on Wednesday.
