Crossing the land border between Gibraltar and Spain is subject to checks. Spain stresses that checks are not politically motivated, it being necessary to ensure strict compliance with EU border regulations to counter the common illicit trafficking issues and that Spain complies with the recommendations from the EU to improve the border crossing. The location of the checkpoint does not conform to the border recognised by Spain. The airport is a military area where civilian aircraft are permitted to operate. Spain claims the airfield is occupied illegally by the UK. The UK claims its sovereignty extends over the isthmus area on which the airfield is built. The UK also claims a three-mile limit in the territorial waters around Gibraltar whereas Spain claims maritime rights to all areas except inside the ports on Gibraltar. UK claims of incursions of Spanish vessels into Gibraltar territorial waters are considered by Spain to reflect routine activity of Spanish ships in their own waters.