The co-pilot has been identified as Hamam al-Hammami, according to three people with knowledge of the situation, including a Gulf and Western diplomat, who spoke on condition of anonymity because they were not authorised to speak to the media.
The United Arab Emirates, which is leading the investigation, said the co-pilot attacked with the FlyDubai cockpit's crash axe and tried to take control of the sharply plummeting plane in a "terrorist attack" Wednesday.
His actions nearly crashed the flight with 182 people on board before passengers and others rushed in and subdued him.
The new details raised questions about how the co-pilot was on the flight. Israel's government has said it has agreements with foreign carriers to keep pilots of nations without diplomatic ties from flying there. Israel and Oman don't have formal diplomatic relations.
FlyDubai hired the co-pilot after Oman Air barred him
Separately, a regional official and a person familiar with the matter said the co-pilot had been barred from flying by Oman over concerns he had adopted extremist views.
The official said he was moved to an administrative job at Oman Air. Both spoke on condition of anonymity to discuss the ongoing investigation.
The co-pilot was later hired by UAE-based airline FlyDubai, the person said. It was not immediately clear to what extent the co-pilot was vetted.
The regional official said the co-pilot was born in the UAE and his mother is Syrian. How he obtained Omani nationality was not immediately clear.
The official also said security agencies from four regional countries were working to establish the co-pilot's motives, aided by the United States and other Western governments.
The Gulf diplomat said investigations were trying to establish whether the co-pilot acted alone or "has any connection with any extremist groups."
A FlyDubai spokesperson said in an email that the airline could not comment beyond its official statements and acknowledged "there are many questions at this stage".
There was no immediate comment from Oman Air, and Oman's government has said nothing publicly in response to repeated questions since the incident.
The incident is a test for the UAE government, which has earned a reputation for effective measures against extremist activities but has also bristled in the past over criticism of security lapses.
Airlines are generally required to carry crash axes in the cockpit that could be used in an emergency to break open a window to escape or break open a panel to access a fire.
The axes are generally stored in the cockpits where the crew can reach them, but they aren't accessible to passengers.
Little else was immediately known about the co-pilot's background. His Instagram account was active until the day of the flight and then deleted.
Israeli Prime Minister Benjamin Netanyahu on Friday said the co-pilot had undergone "Islamist radicalisation," but provided no evidence. There was no immediate comment on Saturday from Israel's government.
The captain who was stabbed has been identified as Indian national Smit Machchhar, who has been hailed as a hero by Netanyahu and Indian Prime Minister Narendra Modi.
The captain, who was badly wounded, has said he used his remaining energy while being attacked to unlock the cockpit door, allowing people who had noticed alarmingly unusual sounds to come in, tackle the co-pilot and stabilise the flight.
The plane made an emergency landing in Saudi Arabia after a descent so extreme that part of the rudder was torn away, and aviation experts have marveled that it didn't crash.
Both the captain and co-pilot were later taken to the UAE. The passengers, most of them Israeli, flew home later Wednesday on a separate plane, to cheers.
- with AP
