A PriorityQueue is a list that always keeps its items sorted based on some rule, like smallest to largest. So, when you take an item out, you always get the one with the highest (or lowest) priority.

Full list of airports allowing UK tourists to use eGates: Paris Charles de Gaulle Airport Paris Orly Airport Bordeaux–Mérignac Airport EuroAirport Basel Mulhouse Freiburg Marseille Provence ...