I've heard the fix for lost luggage (in the USA) is unironically to put a flare gun or starter pistol in checked luggage (note, you do have to declare it and ensure it's properly stored). Why? The airlines get their asses reamed by the ATF if they lose it. If I'm not mistaken, the same laws about firearms in checked luggage apply to a flaregun as they do a Browning M2. If they're lax enough about following firearm laws to lose a flaregun then they're lax enough to lose a high-caliber, fully automatic heavy machine gun.