I took my apple watch on a trip and put it on airplane mode on the plane, I tuned airplane mode off when I got to My destination and it hasn't worked since!! It doesn't communicate with for phone for anything, for example camera remote, weather, ping

Have you tried restarting the watch (hold in button until able to power off, or hold down button and crown to force restart if necessary) or even resetting it if the restart doesn’t help (My Watch > General > Reset)

Have you checked the Settings app on the watch - I found that I had to switch off airplane mode on the watch as well as the phone

Switching on Airplane mode on an iPhone will also turn on Airplane mode on your Apple Watch If you have AirPlay mode set to mirror your iPhone on the watch. but turning off Airplane mode on the iPhone will not turn off Airplane mode on the Watch. You must turn airplane mode off on each device separately.

it also works the other way round. If you turn on airplane mode on the watch it will turn on Airplane mode on the iPhone. But again, each device must be used to turn off Airplane mode.

It doesn't consistently work jointly. I recently took a trip involving frequent airplane mode on and offs. Sometimes changing one device did not change the other. I had some other problems and did a reset/re-pair and it seems to be working now (although i haven't used this setting much since).

Yes, of course you're right. When airplane mode is on on either device, they can't communicate