Also, gates are generally not assigned to flights until 24-48 hours prior to departure. And issuing a boarding pass without a boarding gate is a bit of a waste. in many airports in many countries, the gates aren't assigned until an hour or two before boarding begins.

The 24-hour check-in window is an industry standard that serves several logistical and security purposes. First, it allows airlines to finalize their "weight and balance" calculations; by confirming exactly who is showing up, they can better estimate fuel needs and cargo distribution. Second, it relates to security protocols like the TSA's Secure Flight program, which performs final manifest checks against "No Fly" lists shortly before departure. From a revenue perspective, the 24-hour mark is often when airlines begin the "clearing" process for upgrades and standby lists. It also gives the airline a chance to resell seats from "no-shows" or people who haven't checked in, helping them maximize load factors. For passengers, the 24-hour mark is crucial because it often dictates your boarding position (especially on Southwest Airlines) or your ability to select the best remaining seats. While some airlines allow "auto-check-in" or earlier windows for premium members, the 24-hour rule remains the universal point where the flight transitions from a future booking to an active operational event, allowing ground crews to prepare the final gate manifests.