Generally, yes—checking in as early as possible (usually 24 hours before departure) gives you the best chance of securing a preferred seat among the remaining inventory. For airlines that use an open-seating model, like Southwest once did (though they transitioned to assigned seating in late 2025/2026), check-in time directly determines your boarding position and thus your choice of seat. For traditional carriers like Delta, United, or British Airways, the "good" seats (aisles, windows, and exit rows) are often snapped up by elite members or those who paid to reserve them at booking. However, at the 24-hour mark, airlines often release a block of previously "held" seats or seats that were unassigned due to upgrades. By being one of the first to check in via the app, you can often "snag" an exit row or a seat closer to the front that just became available. Some ultra-low-cost carriers also use an algorithm that assigns the "worst" seats (middles) first to encourage people to pay for a change, so checking in very early or very late can sometimes be a strategic gamble to get a better spot for free.