Here?s a safety tip? Bring two leashes. That way you?ll have a spare when you misplace one. Cats are notorious for doing Houdini-like escapes from their collars. A harness is much more secure, especially the ones that will adjust according to the amount of tension placed against it. The harder a cat pulls the tighter and more secure the slip harness becomes. Travel crates human versions of dens, make great containment devices and many cats enjoy hiding out in them while traveling.