 Smuggling between Gibraltar and Spain remains a source of tension between the two governments and occasionally leads to long delays for vehicle traffic crossing the border during Spanish Civil Guard crackdowns.The ongoing political dispute with Spain has also hampered the development of transport links.It was not until as recently as December 2006, following the signing of the Cordoba Agreement, that direct flights between Madrid and Gibraltar were re-established, Air traffic had previously been obstructed (at previous times, flights to and from Gibraltar were not even permitted to fly over Spain) as the Spanish did not recognise the British sovereignty over the land where the airport is located and demanded a joint operation of it and the right to treat the airport as a domestic (Spanish) facility.