As a general rule, most airlines will NOT automatically check your luggage through for an overnight connection. You will normally need collect your luggage when you land, and re-check it the following morning. This is normally a good thing as it allows you access to your luggage for your overnight stay.

There is no universal rule; it depends on your airline, ticket type, and the layover duration. If you are on a single ticket (e.g., London to Tokyo via New York), many airlines like Delta or Singapore Airlines will "check through" your bags to the final destination, meaning you won't see them until you arrive. However, some airlines have strict time limits; for example, United usually only holds bags for layovers under 12 hours, and American Airlines under 16 hours. If your layover exceeds these limits, you must collect your bags. Additionally, if you are entering a country like the USA or Canada from an international flight, you almost always have to pick up your luggage to clear customs at your first point of entry, even if it's an overnight stay. Always check your bag tag at initial check-in to see the final destination code.