I've used them on some TATL flights...not on domestic flights. I've lost about half of them...some gone altogether, some unlocked but hanging from the zipper handle (sometimes a note inside, sometimes not) and some locked where I left them. I never plan that I will have the lock at my destination...if I do, I win...it's a crapshoot. I take an extra lock for use when I leave the bag at my hotel's bellman or if I leave something in the suitcase in my room.