A British passenger spoke of her frustration after flights were grounded at a US airport while authorities searched for a man who walked through a screening checkpoint exit into the secure side of a terminal.

Passengers were being re-screened after the security breach, an air safety official said.

A man was seen at Newark Liberty International Airport walking down an exit lane at Terminal C, said Transportation Security Administration spokeswoman Ann Davis.

Screening was halted in the Continental terminal at the New Jersey airport while authorities looked at surveillance tapes to identify the man.

Passengers were then evacuated from the secure side of the terminal and moved to the open side to go through screening again to ensure that every passenger boarding a plane out of the terminal was fully screened, Ms Davis said.

Briton Alison Day, 47, of York, was supposed to leave for Manchester, on Sunday night. She was travelling with a party of seven including an 18-month-old child and five-year-old.

"I'm not angry that this is happening, but I'm angry that there was a lack of organisation," she said.

She said her party, heading home after a Caribbean cruise, was escorted out of Continental's lounge but given no further instructions.

Continental spokeswoman Susannah Thurston said it's an airport security issue not involving the Houston-based airline.

A spokesman said the Port Authority of New York and New Jersey was assisting with the security breach, and Ms Davis had no update on the man who walked through the exit.