The motive of the Omani copilot who stabbed his captain on a flight to Israel, causing the plane to plummet dangerously and forcing it to land in Saudi Arabia, remained unknown on Thursday as investigators across the region raced to learn more. Israeli passengers who were on the FlyDubai aircraft carrying 174 people 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 stabilised a descent so sharp that the plane’s rudder was torn away.