In times I've had to transport firearms in checked luggage in the US, the guidelines usually required a locked, hard-sided container. Assuming you didn't have a lock at the time, at least they were nice enough to use zip-ties as a substitute. Of course I haven't done that in at least 7 years... with airlines and air travel as messed up as they currently are, they might not be so helpful.

But as for zip ties themselves, I like putting them on luggage in addition to the TSA locks. Not to stop them from opening my luggage, rather just to know for sure IF my bags have been opened.