Technically, the duration of a layover is defined by its length relative to a stopover. For domestic flights in 2026, a layover is generally considered any connection lasting less than 4 hours. For international flights, a layover can last up to 23 hours and 59 minutes. Once a connection hits the 24-hour mark, it is officially classified as a "stopover," which may trigger higher ticket taxes or require you to collect and re-check your luggage. Airlines often allow you to book "long layovers" (10–20 hours) intentionally, which is a popular travel hack for seeing a city without paying for a separate flight. In some hubs like Singapore, Doha, or Istanbul, the airline may even offer free city tours or hotel stays for layovers exceeding 8–12 hours. However, always check your transit visa requirements; even if you stay airside, some countries require a "Transit Visa" if your layover exceeds a certain number of hours or involves a change of terminals.