Air guns, replicas and long blades on a plane
For departures from the United States, TSA keeps air guns, slingshots, realistic firearm replicas and long blades out of carry-on baggage. Checked-bag conditions differ by item. Identify the mechanism and pack any gas, ammunition or sharp shaft under its own rule.
Air guns and slingshots
TSA lists compressed air guns, including paintball markers, as checked-bag items only when the compressed-air cylinder is detached. A slingshot also belongs in checked baggage. Keep projectiles contained and ask the airline whether it accepts the complete kit; gas and ammunition have separate rules.
Realistic firearm replicas
A realistic replica cannot go through a US checkpoint in carry-on. TSA lists it for checked baggage, while a functioning gun, starter pistol or air gun needs assessment under its own entry. Check what the prop actually does before packing it, and confirm airline and destination requirements.
Long blades and spear guns
TSA excludes swords, including fencing foils, from the cabin. Sheath or securely wrap a saber or sword in checked baggage so the tip cannot injure baggage handlers. A spear gun is also checked-bag only: unload it, secure the shaft and cover its point. Measure the full case against the airline's baggage limits.
Source: TSA: What Can I Bring?.