Fun fact for you, airlines (and some train companies) have a special exemption to charge cards differently to normal merchants. This means that even cards which are ‘online only’ should work on planes. It’s why stuff like this can happen http://www.telegraph.co.uk/news/2017/01/29/mid-air-credit-card-scammers-given-suspended-jail-sentences/
And while we’re on the subject of transactions on planes, it’s really important to remember that you won’t get live spending notifications. In fact, your card can be charged up to six months after the flight 
Some airlines are worse at this than others, but if you see a charge on your Monzo from an airline, it could well be that burnt tasting coffee from several months ago 