The unticketed passenger managed to get through the standard Transportation Security Administration screening, and somehow evaded identity verification and boarding status stations.

Port of Seattle Police said the stowaway then “gained access to the loading bridge without a scanned ticket at the gate,” according to CBS News.

The stowaway was identified on the plane while it was taxiing for takeoff, and the aircraft returned to the gate. The stowaway, who was not named, managed to flee from the plane, but was discovered in a terminal restroom.

The Port of Seattle said the stowaway was booked on a charge of criminal trespassing and arrested.

“As there are no matters more important than safety and security, Delta people followed procedures to have an unticketed passenger removed from the flight and then apprehended,” a Delta spokesman told ABC News.

TSA said it would independently review the circumstances of the incident to determine how the stowaway made it through its travel document checker station at the airport without being identified as a person without a ticket.

Delta said it is conducting its own investigation to find out what loopholes the stowaway used to get onto the plane without a ticket.

In November, Russian national Svetlana Dali managed to get onto a Delta plane at John F. Kennedy International Airport in New York and traveled to the Charles-de-Gaulle International Airport in Paris without a ticket.

Dali was detained and returned to the United States by French officials once they discovered she did not have documents to enter their country.

She was arrested upon her return to the United States and arrested again this month when he cut off her ankle monitor and tried to escape to Canada on a Greyhound bus in Buffalo, N.Y.