The Transportation Security Administration found three firearms in carry-on luggage in the past three weeks at Billings Logan International Airport.
TSA officers found a 9 millimeter Glock G19 semi-automatic pistol loaded with 15 rounds, and one in the chamber for a passenger heading to Dallas-Fort Worth on Tuesday.
Security officers also found a .40 caliber Glock 23 handgun loaded with 13 rounds from a passenger heading to Denver on March 19.
A 9 milimeter Sig Sauer P290 compact pistol with six rounds was found for a traveler heading to Las Vegas on March 26.
The TSA says that firearms may be taken on commercial flights only if not loaded, if it's packed and locked in a hard-sided case, and it's placed in checked baggage.
Passengers need to declare the firearm, ammunition, and firearm parts at the ticket counter.
"TSA will levy a civil penalty against every passenger who brings a firearm to the security checkpoint," said Lorie Dankers, TSA spokesperson for Montana. "It's an expensive mistake. Law enforcement is always notified when we discover a firearm at the checkpoint. So you have that inconvenience of needing to go through that process as well with the airport police. So there's really one way around that. And that is travel legally with that firearm and check luggage."
Each passenger was allowed to board the flights without their guns.
Dankers said there is no evidence of a connection among the three incidents.