Generally, most airports do not allow passengers to go through security the night before their flight. This is because security checkpoints usually close during late-night hours when the airport is less busy.

Whether you can go through security the night before a flight in 2026 depends entirely on the specific airport's operating hours and the timing of your boarding pass. In most large, 24-hour airports like LAX or London Heathrow, you can clear security the night before if you have a valid boarding pass for a flight departing the next morning (usually within 24 hours). This is a common strategy for budget travelers planning to "sleep airside" to save on hotel costs. However, many medium and small airports close their security checkpoints overnight, typically between 11:00 PM and 4:00 AM, meaning you would be forced to stay in the "landside" public area until the morning. Another hurdle is checked luggage; most airlines will not accept checked bags more than 2 to 6 hours before a flight. Therefore, if you have a checked bag, you cannot clear security until the bag is dropped. If you are traveling with carry-on only and the airport is a 24-hour hub, you can generally clear security as soon as your mobile boarding pass becomes active (usually 24 hours before departure).