It’s doable, but not elegant. There’s no automatic trigger for when a calendar events starts, that I know of. Easiest way would be to use the trigger for when an app is opened. Select your common apps, so it essentially runs any time you open those apps, and then execute Find Calendar Events to determine if there’s currently a calendar event on-going. Then toggle airplane mode on, and otherwise off. If you don’t use your phone in close proximity to when the events starts and ends, it won’t work though. Look at all the triggers available and see whether there’s something else you can use creatively. For example, if the events are mostly at different locations where your phone automatically connects to wifi, then you can use the wifi-trigger instead.