Whether you need to check in again for a connecting flight depends primarily on if your journey was booked on a single ticket (PNR) or as two separate "self-transfer" flights. If you booked a single itinerary with a legacy or major airline, your bags are typically "checked through" to your final destination, and you will receive all your boarding passes at your initial departure airport, meaning no second check-in is required. However, if you are connecting from an international flight to a domestic one (especially in the USA or India), you must often collect your luggage after immigration, clear customs, and "drop" it at a re-check counter, though you usually don't need a new boarding pass. If you booked two separate flights on different airlines (often the case with budget carriers like Ryanair or Spirit), you must exit the secure area, collect your bags, and go through the full check-in and security process as if you were starting a brand new journey.