My assumption is that location based security is used to check your location (the location of your phone) vs where your ‘card present’ transactions are being made. If the transaction’s not being made in the same place as your location, it would be more likely to be flagged as potentially fraudulent. So it should be helpful if you switch that setting on.
But if you don’t have a data connection, Monzo will use other methods to check whether the transaction is fraudulent & their checks are designed in a way that should stop the transactions from being flagged -
But following on from Dom’s comments in the above post, since Monzo’s database of airport locations is probably still incomplete (as they’ve only started building it relatively recently), it might be worth messaging the support team via the in-app chat, to explain your situation & see if there’s anything else that they can do, to make it less likely that your transactions are blocked.
The good news is that Monzo’s customer support response times are much quicker than your average legacy bank’s & using the chat removes a lot of hassle when it comes to contacting them. So even if you do run into issues, you should be able to get them resolved much sooner than usual. Hopefully you won’t though!