If you want to see if your bags have been opened or not at an airport just lock together the zippers with inexpensive cable ties.
We know that TSA screens every passenger’s baggage before it is boarded on the belly of your flight. While their sophisticated equipment lets them to electronically screen most bags, there are random moments when they need to physically inspect a piece of luggage. TSA has worked with several companies to develop locks that can be opened by security officers using universal “master” keys so that the locks may not have to be cut. These locks are available at airports and travel stores nationwide. Of course if you have one of these keys, the lock is pointless. I prefer keeping it simple myself.
This way if the zip tie is removed once you get to your destination you know the TSA has opened your luggage. Now, if you discover something is missing from your luggage you can file a claim with your insurance with proof. TO make things easier, take a photo of the contents of your bag with your smartphone and then you have more proof of what was in your bag during transit.