There is no flight mode option on the Assure Touch watch phone. You can simply power off the watch when going on a flight by Tapping on Manage in the App and select Power of the watch remotely. You can set it to automatically power back on at a set time. Alternatively when you reach your destination you can power back on the watch and wait a couple of minutes for the watch to activate.
Remember if you have changed time zones, update the watch time in Manage, Device Time.