Over 700 airlines operate globally, and each has different fee types, baggage cost rules, and seating policies. But what helps you make sense of it all? It’s actually your boarding pass.

The letters on your pass reveal your ticket class: first class, business class, coach, or discounted economy class. SSSS shows the TSA selected you for additional screening. STBY means you don’t have a confirmed seat.

And then there’s something called SEQ. That dictates the boarding order, but it really shows the order in which the boarding passes were issued. That order determines whether you stay on the plane or get bumped if they oversell the flight.