We always carry extra euros/pounds for tipping at the airport for porters who carry luggage etc. My husband gets assistance at the airport either a wheelchair or buggy and we always give a tip,the service is excellent so it is worth giving especially as some of these porters don't be paid very well. If a porter carries your luggage to the room as they do on cruises they deserve a tip, five euros etc is
reasonable, Varies from place to place and depending on how you appreciate the service.