Yes, you can leave the airport during an overnight layover, but your ability to do so depends on your nationality and the visa requirements of the transit country. If you are a U.S. or Canadian citizen transiting through most of Europe (the Schengen Area), you can typically walk out of the airport with just a passport stamp. However, in 2026, you must ensure you have the necessary digital authorizations, such as an ETA for the UK or ETIAS for Europe, if applicable. For an international layover, experts recommend a minimum of 8 to 10 hours to make exiting worthwhile, as you must clear immigration, travel to the city, and return in time to clear security again. During an overnight stay, many airports (like Singapore Changi or Doha) even offer specialized transit hotels or city tours. It is vital to confirm if your checked luggage is "checked through" to your final destination; if not, you may need to store it in a luggage locker. Always aim to be back at the airport at least 3 hours before your connecting flight to avoid any boarding mishaps.