The woman was detected on board Delta Flight 264, which departed Kennedy for Charles de Gaulle Airport just before 11 p.m.
In a passenger's video taken after landing in Paris this morning the pilot for Delta Flight 254 can be heard announcing that police have arrived and for everyone to stay seated.
"While we sort out the extra passenger that's on the plane," the pilot said.
A flight attendant eventually figured out that a woman was staying in the plane's bathrooms for unusual periods of time.
"TSA can confirm that an individual without a boarding pass completed the airport security screening without any prohibited items. The individual bypassed two identity verification and boarding status stations and was able to board the aircraft," TSA said in a statement.
Federal law enforcement is investigating the incident.
"Nothing is of greater importance than matters of safety and security. That's why Delta is conducting an exhaustive investigation of what may have occurred and will work collaboratively with other aviation stakeholders and law enforcement to that end," Delta said in a statement.
A TSA spokesperson released a statement saying: "TSA can confirm that an individual without a boarding pass completed the airport security screening without any prohibited items. The individual bypassed two identity verification and boarding status stations and was able to board the aircraft. Law enforcement is involved for anything further on this."
The passenger who took the video said flight attendants became suspicious when the passenger was going from one bathroom to another.
But that didn't happen until they were practically in Paris.
"For 7 hours on a flight, she's coming out, going into different toilets, and just before landing, then the flight attendant thinks to themselves, what is it with this woman going between toilets? Why doesn't she ever go to her seat? There's a failure here that frankly, 33 years flying worldwide airlines, that it's inconceivable to me," said JP Tristani, Former Commercial Pilot.
Eyewitness News spoke to former commercial pilot JP Tristani about how this could happen: a stowaway without a boarding pass getting through at least 3 checkpoints and onto a full transatlantic flight on one of the two busiest air travel days of the year.
"Even standby passengers just don't get on board. You have to go through the gate agent," Tristani said.
"And on a day like Thanksgiving, Christmas, highly traveled, you also have, generally speaking, packed flights, no seats available or aircraft are going out full. We have a gross failure here of security right on down the line," Tristani said.
There's been at least one stowaway case in which someone used a picture or screenshot of someone else's boarding pass to get on a flight. It's not clear if this passenger used something like that. Because she went through TSA screening, she did have a valid ID.
The FBI has joined the investigation tonight.
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