I have used Optech rear Nikon lens caps for about five years, and none have ever come occ spontaneously. they use a neoprene seal which makes a tight 'grab' on the metal tabs.
So far, my Lowepro magnum bag has fit under every seat ( AA, United, KLM, Pioneer, Southwest,Horizon, American Eagle, Lufthansa, Air France) with many different fuselage types. No Bombardier yet.
A
I found that the Nikon 24-120 AFD VR on my D810 worked perfectly, Raising the ISO to 800 or (rarely ) 1200 permitted any exterior or interior images. The circualr polarizer occasionally was used outside . I travel with several batteries, charge them at night, I carry a collapsible carbon fiober monopod,, utilize a quick release mounting system, and use it when I can. No problems anywhere.
Film is costly , unreliable ( outdated, not kept cool, perhaps previously x-rayed), and processing is infrequent, and of greatly varying quality in the third world. IN the UK and europe, less risky.
shoot digital and set the camera to process it as film, or set computer in postprocessing to process a film. Works for me.