Yes, you are generally allowed to exit the airport during a layover, provided you meet the legal entry requirements of the country you are in. For domestic flights, exiting is simple; you just walk out, but you must pass through security again to return. For international flights, the rules are stricter. You must pass through Immigration and Customs, which requires a valid passport and, depending on your nationality, a visa or transit visa (like an ESTA for the US or an eTA for the UK). It is crucial to monitor your time; experts recommend at least a 6-hour layover for domestic and an 8-to-10-hour layover for international stays to account for the time it takes to deplane, clear immigration, travel to the city, and return through security. Always check if your airline's policy allows for "stopovers," as some budget carriers may treat an exit as a forfeited second leg if not properly coordinated.