TSA officers found the concealed weapon "behind the lining of a suitcase" during screening operations of checked baggage at the airport.
The assault rifle was found with a high-capacity magazine and four boxes of hollow-point bullets, TSA said. Officers also found three magazines -- one of which was fully loaded -- and two additional boxes of ammunition.
"Our TSA officers are very skilled at detecting firearms and other prohibited items," Tom Carter, TSA's Federal Security Director for New Jersey said in a press release. "This was an incredibly good catch on the part of our officers because the traveler attempted to evade detection by concealing the items beneath the lining of his suitcase."
TSA said the Port Authority police were notified about the weapon and subsequently tracked down the woman, who was arrested along with her traveling companion.
Editor's note: This story has been corrected to reflect a woman was arrested.