Another disturbing incident involving Frontier Airlines has erupted at Denver International Airport — this time after passengers were abruptly forced off a flight when a gun magazine was allegedly discovered onboard just moments before departure, triggering a massive security response and renewed fears over airport safety failures.

The frightening situation unfolded Sunday night aboard Frontier Airlines Flight 4765, which was scheduled to depart Denver for Phoenix. According to airline officials, the aircraft was preparing for takeoff when crew members discovered an ammunition magazine inside the plane.

Within minutes, the atmosphere inside the cabin reportedly shifted from routine boarding to confusion and fear.

Passengers were suddenly ordered to deplane while armed officers and airport security teams swarmed the gate area. Travelers were escorted off the aircraft and transported by bus to another screening area, where every passenger underwent additional TSA checks as authorities searched for any possible weapon connected to the magazine.

Officials later confirmed no firearm was found onboard, but the incident immediately sparked alarm because it came only days after another Frontier Airlines jet at the same airport struck and killed a trespasser who was sucked into an engine during takeoff.

According to Frontier Airlines, preliminary findings suggest the magazine may have belonged to a law enforcement officer who accidentally left it behind after a previous flight. However, federal investigators have not yet publicly confirmed how the item bypassed security procedures or remained undiscovered until shortly before departure.

The FBI and TSA are now involved in the investigation as questions intensify over security breakdowns at one of America’s busiest airports.

Passengers described the situation as chaotic and deeply unsettling.

One traveler told local media that nobody initially explained why the plane was being evacuated, leaving confused passengers wandering through the airport after repeated security screenings. Another passenger claimed Frontier later canceled the flight entirely after the crew exceeded legal duty hours because of the lengthy delay.

Some frustrated travelers also complained that the airline refused to provide full refunds despite the hours-long disruption, with one passenger reportedly receiving only a $15 meal voucher after the cancellation.

Online reaction exploded almost immediately after news of the incident spread.

On Reddit, users mocked the growing string of Frontier-related incidents at Denver Airport, with some joking that the airline was having “the worst week imaginable.” Others expressed outrage that an ammunition magazine could allegedly make it onto a commercial aircraft at all, especially after heightened scrutiny surrounding airport safety in recent days.

The discovery has also reignited criticism toward TSA screening systems after a union spokesperson reportedly admitted the magazine appearing onboard suggested security officers may have missed it during passenger screening.

While authorities insist there was never an active shooter threat, many passengers say the psychological impact was impossible to ignore — especially so soon after the horrifying jet-engine tragedy that left Denver International Airport under national scrutiny.

And now, investigators are facing another uncomfortable question:

How did ammunition connected to a firearm end up inside a passenger aircraft at one of the most heavily secured airports in the United States only days after another catastrophic Frontier Airlines incident?