Hey there,
this sounds like the famous sudden death of the fairphone 3. There are already some threads about his issue, this one is quite a comprehensive one.
Before you dig into it I would recommend you to make sure there is no other problem. Are there any reactions from the phone when you try to charge it? Did the charging port make problems earlier? Do you have a voltmeter to check the voltage of the battery to make sure it has enough power to start your phone? Did the battery really expand during the flight or might it have “grown” earlier (when did you check it the last time)?
Hope this helps,
Clemens