An investigation has been launched into how a young Bulgarian man boarded the wrong flight at Athens International Airport and was eventually discovered by passengers rather than security or airline staff. It was revealed yesterday that the unnamed man boarded a flight for Copenhagen although he had a ticket for a different destination. Officials want to find out how he passed through two security checks without staff noticing that he was headed for the wrong flight. It only emerged that the Bulgarian was on the wrong airplane when passengers noticed that he changed seats several times after boarding the aircraft. They notified the cabin crew and airport security staff boarded the airplane and removed the passenger. Sources said the young man was given an eight-month suspended sentence for breaching air travel safety laws.