Unfortunately indeed a familiar story. Some of these folks are serial offenders it seems.
Turhan Jamarius Lamons (he apparently is a con artist with several aka's according to court documents) did the phony bomb threat while working as a flight attendant on AirTran in 2001. He got fired and got another F/A job with Comair. There he set a fire in the lav:
Lamons was sentenced in 2006 in U.S. District Court in Rome, Ga. on charges of intimidation of a flight crew by use of fire, damaging an aircraft by fire, use of fire in the commission of a felony crime and giving false information concerning the destruction of an aircraft.
According to the information presented in court, on the evening of May 8, 2003, Lamons, who was working as the sole flight attendant on Comair flight 5491 from Atlanta to Huntsville, Alabama, set a fire in the lavatory of the aircraft. When Lamons reported to the Captain that there was smoke of unknown origin in the lavatory, the Canadair Regional jet was forced to make an emergency landing at Rome’s Richard B. Russell Regional Airport about twenty minutes after takeoff.
Suspicion focused on Lamons after the Rome Fire Marshal, Vann Baxter concluded that the fire was set deliberately and the investigation showed that he was the only person who entered the lavatory during the brief flight. Lamons also had made numerous conflicting statements about the fire and his involvement with it. The case was investigated by the Floyd County Police and Special Agents of the FBI.
Prior to the above charges, Lamons was convicted in March of 2005 of calling in a bomb threat in September of 2001. In that conviction, Lamons was charged with maliciously conveying false information concerning an attempt to damage a civil aircraft and committing an act of violence against aircraft passengers.
Those charges stemmed from a call he made to AirTran Airways at Hartsfield-Jackson Atlanta International Airport. The false information conveyed was that “Everyone on board flight 278 is going to die.” Although Lamon was convicted in those charges, he had not been sentenced in court due to delays.
Airline terrorist now being housed at Polk County jail in Cedartown, Ga. | Examiner.com
Another possible 'serial hero' case of a flight attendant setting a fire in the lav from 2008:
A flight attendant who started a fire on an aircraft mid-flight just so he could 'play the hero' by putting it out has been jailed for more than six years.
Eder Rojas, 23, risked the lives of 72 passengers and four crew members, when he set fire to paper towels in the plane's rear bathroom while he was working on the Compass Airlines flight.
Investigators accused Rojas, of Woodbury, Minnesota, of starting the fire because he was unhappy about working the route from Minneapolis to Regina, Saskatchewan.
Prosecutors said about five weeks before the Compass flight incident in May 2008, Rojas was aboard another flight that was forced to make an emergency landing in Wisconsin because of a bathroom fire.
Rojas allegedly helped put out the fire. No charges have been filed in that case.
Flight attendant jailed for setting fire to an aircraft so he could 'put it out and play the hero' | Daily Mail Online
Keeping folks with a bad past from working on the plane is not as simple as it sounds from what I see.
In the U.S. airlines are now very skittish about releasing information about former employees, even those terminated for cause under the most egregious circumstances. Often someone is allowed to 'resign' to avoid further litigation in a very few recent cases that I am aware of anecdotally.
And, airline worker background investigations seem to be pursued less vigorously in the wake of a 2013 EEOC lawsuit claiming that background checks may have been used as a form of discrimination against groups more likely to have felony convictions:
EEOC Files Suit Against Two Employers for Use of Criminal Background Checks