Can I leave the airport during a long layover?

Yes, on domestic itineraries. There's no legal or airline rule preventing you from leaving the airport during a layover. Your boarding pass for the next flight is already issued, and you're free to come and go. Just make sure you leave enough time to get back through security.

Budget at least 2 hours to be safe: time to leave the airport, do what you need to do, return, get through security, and reach your gate before boarding starts (usually 30-40 minutes before departure). At airports with easy transit connections — like SFO (BART), ORD (Blue Line), DCA (Metro), or MSP (Blue Line) — this works well for layovers of 4+ hours.

Things to keep in mind: if you checked bags, they'll be transferred automatically to your next flight — you don't need to collect them. If your first flight is delayed and your layover shrinks, the airline won't wait for you if you're outside the airport. And for international layovers, leaving the airport may require a visa depending on the country, even for a few hours.