The passengers disembarked from Delta Flight 3 from Heathrow Airport Monday in an area of Terminal 4, which has domestic baggage claim, a passenger on the flight, Andrew Rostron said.
Airport employees realized the passengers were in the wrong place. They were then taken through immigration and customs, CBS News reported.
Any passenger who had a carry-on bag, though, would have been able to walk right out of the airport, Rostron said.
"A small number of customers off Delta flight 3 from London to New York's Kennedy International Airport were able to bypass customs screening. Delta is working with the Port Authority as well as Customs and Border Protection and is looking into the matter. Customer security is of vital importance and Delta makes every effort to follow appropriate procedures," the airline said.