Israeli Prime Minister Benjamin Netanyahu said Israel is investigating whether the co-pilot accused of attacking a Flydubai captain and trying to crash the aircraft was sent by others. “We are investigating whether he was sent, and whoever sent him will pay a very heavy price,” Netanyahu said Friday. He said the attacker underwent Islamist radicalization and intended to crash the plane with its passengers aboard.

Flight FZ1073, carrying 174 people from Dubai to Tel Aviv on Sept. 30, landed safely in Tabuk, Saudi Arabia, after passengers and crew subdued the co-pilot and additional Flydubai pilots aboard took control. Saudi Arabia’s initial investigation found that the co-pilot assaulted the captain. Both pilots were transferred to Abu Dhabi after medical clearance, and the passengers reached Israel on a replacement aircraft.

UAE presidential adviser Anwar Gargash earlier Friday called the attack a “dangerous terrorist act.” The UAE investigation is examining possible terrorist motives, prior planning or direction. Indian Captain Smit Machchhar told Prime Minister Narendra Modi that he opened the cockpit door while wounded and still being assaulted, allowing others to intervene. Flydubai has suspended flights to and from Israel while the investigation continues.