After Delta Air Lines said a person was able to board a flight in Seattle without a ticket, a source with knowledge of the situation tells NBC News that the passenger was able to bypass security I.D.

The person, who boarded the flight without a ticket, was detected as the plane was preparing to take off for Hawaii on Christmas Eve.

Delta Air Lines said it discovered a second passenger without a ticket this month, this one actually getting on a plane bound from Seattle to Hawaii, officials said.