The grenade launcher was found in pieces and unassembled in a man's checked bag at Lehigh Valley International Airport, TSA Public Affairs spokesperson Lisa Farbstein said in a Twitter post.
In a press release, the TSA said that the launcher belonged to a Florida man and that it set off alarms as it was passing through the airport's security equipment.
The unassembled pieces of the grenade launcher included a barrel, trigger, sights and a grenade replica, the TSA said.
"When assembled, the launcher was determined to be non-functioning and the grenade an inert replica," Farbstein wrote, adding, "(Thank goodness!)"
Pictures from the TSA indicate the device was over 3 feet long when assembled.
The man, from St. Augustine, Florida, was detained by police for questioning, the TSA said, adding that he told law enforcement he believed that he could bring the military rocket-propelled grenade launcher and replica grenade on his flight in a checked bag.
"However, no realistic or replica weapons of military nature are permitted to be brought onto airplanes," the TSA press release said.
Bringing a weapon or replica weapon to the airport can get you a civil penalty up to $13,000 under TSA rules.
While the grenade launcher was confiscated, the TSA confirmed that the Florida man did make it onto his flight to Orlando Sanford International Airport.