Boston Logan International Airport (BOS) is technically open 24 hours a day, but its operational facilities, such as ticket counters and security checkpoints, have specific hours. Most TSA security checkpoints at Logan open between 3:30 AM and 4:30 AM, typically timed to be ready one hour before the first scheduled departure of the day. Airline ticket counters generally open around the same time, usually between 4:00 AM and 5:00 AM. If you have an early morning flight, it is important to note that you cannot pass through security until the TSA lanes open, and you must remain in the "pre-security" public areas if you arrive during the night. The airport's retail and dining options also vary, with most opening between 5:00 AM and 6:00 AM. For domestic flights, the airport recommends arriving 2 hours early, while for international travel, 3 hours is advised, especially since Terminal E (International) can experience significant morning and evening "banks" of flights.