For the vast majority of travelers in 2026, online check-in is the superior choice. Most airlines open online check-in 24 hours before departure, allowing you to secure your preferred seat early and receive a digital boarding pass. This allows you to skip the long ticket counter lines and head straight to security if you only have carry-on luggage. Furthermore, some low-cost carriers (like Ryanair or Frontier) now charge a significant "service fee" (often $25–$50) if you wait to check in with an agent at the airport. However, checking in at the airport counter is better in specific scenarios: if you are traveling with a lap infant, have a complex visa/residency situation that requires physical document verification, or are checking oversized sports equipment. Additionally, if the airline's app is glitching or you need a paper boarding pass for your records, the airport kiosk is a reliable backup. Generally, checking in online "buys" you extra time and peace of mind on your travel day.