29 year old Omani co-pilot accused of stabbing the captain of a Dubai–Tel Aviv Flydubai flight has been identified as Hamam al-Hammami.
The answer to how a flagged pilot gets back into a cockpit is contained in one word in the timeline: he resigned. That is how it happened and is common in many industries. Oman Air found the problem, decided against dismissal, moved him to a desk job.
He than left on his own. This means his employment record shows a voluntary departure with no termination, no cause, no adverse finding attached to his name.
He was never charged, so no criminal record was ever created.
That means a standard background check in a neighbouring country comes back clean, because there is nothing in any database to find.