Your luggage quota will vary depending on the airline that you fly. For example, if you fly from Heathrow Airport (LHR) to Belgrade Airport (BEG) with Air Serbia, you can take one item of cabin baggage. However, if you want to take a checked item, you will need to pay extra. Wizz Air UK on the same route allows only allows a small carry-on bag, with checked and cabin baggage costing extra. Flights with Lufthansa on this route allow you to bring one checked item and one cabin bag.