An ongoing dispute between Spain and the UK about the sovereignty of Gibraltar could obstruct any Brexit deal granting the UK’s aviation industry open access to EU skies if it were to apply to Gibraltar’s airport, Spanish diplomats have said, according to press reports.

Spain has indicated that it would block UK access to the open EU aviation market, unless Gibraltar’s airport is carved out from any post-Brexit deal, according to the Financial Times.

“Any EU agreement with the UK on aviation cannot apply to the airport of Gibraltar,” it quoted a Spanish diplomat as saying. “A deal that is applicable to the airport of Gibraltar would imply recognition of the legal right of the UK to the territory.”

Gibraltar is a British overseas territory, but that has long been contested by Spain, which claims sovereignty over the peninsula.

The dispute over Gibraltar’s airport has already stalled three separate pieces of EU aviation legislation, including proposed revisions to regulations governing passenger rights, airport slots and air traffic management.

Those have each been held up due to the ongoing dispute between both countries about whether such regulation should apply to Gibraltar’s airport.

Chris Grayling, the UK’s secretary of state for transport, said in a speech at the end of January that securing the best deal for the country’s aviation industry is a priority following Brexit.

Retaining membership of the European Common Aviation Area should be a key pillar of such a deal, according to lawyers who spoke to GTDT Aviation Law News, although that would require unanimous support from all member states, Spain included.

A post-Brexit bilateral open skies agreement between the UK and the EU is seen as a less advantageous option by most in the UK’s aviation industry, although that too would require support from Spain.

A spokesperson for the government of Gibraltar said it had not heard anything on the subject.

“The negotiations for the United Kingdom’s exit from the European Union have not even commenced,” she said.

Spokespersons for the UK Department of Transport and Spain’s Ministry of Foreign Affairs were unavailable for comment.

The government of Gibraltar has previously said that all EU civil aviation legislation should apply to its airport “without prejudice to the respective legal positions of the UK and Spain about the land on which the airport is built”, or alternatively, Gibraltar should not be explicitly named in any proposed legislation.

“Gibraltar airport is an airport of the EU and must not be discriminated against on the basis of an illegitimate sovereignty claim,” it said. “The bottom line is that the solution lies in the application of EU law and, by virtue of EU law, Gibraltar is automatically included.”

The Spanish and UK governments previously agreed – under the 2006 Cordoba Agreement – that the dispute over Gibraltar would not delay the enactment of EU aviation legislation.

The UK argues that Spain has ignored its commitments under that agreement, although the Spanish government maintains that the airport illegally occupies disputed land between Gibraltar and Spain. It sees the inclusion of the airport in any aviation negotiations as legal recognition that the land belongs to Gibraltar rather than Spain.

Anna Anatolitou, a partner at Ince & Co in London, said the Gibraltar dispute cannot be underestimated as an obstacle in Brexit aviation negotiations.

“It is an enormous issue. The political dispute between Spain and the UK over Gibraltar – and in particular, the status of the airport – has brought most EU aviation legislation in recent years to a complete standstill. The key thing holding that legislation back is the Gibraltar dispute. If not addressed early on, it will be an enormous stumbling block,” she said.

“Any deal giving access to EU open skies requires the unanimous consent of all the other EU member states.”

Thomas van der Wijngaart at Clyde & Co in London said there is a “real risk” that the Gibraltar issue could affect a Brexit aviation deal.

“Spain continues to insist on the exclusion of Gibraltar airport from various pieces of proposed EU legislation. There appears to be a general reluctance at [European] Council level to interfere with matters of sovereignty between two member states. I anticipate that the same issues could arise in the Brexit context,” he said.

“To the extent that UK access to the European Common Aviation Area can be negotiated, I anticipate that Spain would seek the usual carveout for Gibraltar, in the absence of which it may attempt to scuttle any wider aviation deal. It will be interesting to see how the UK government balances the protection of territorial sovereignty with the need for market access.”

Philippe Ruttley, who heads the EU group at Ince & Co in London, meanwhile said Gibraltar will not just be a stumbling block in a post-Brexit aviation deal, but also during the UK’s wider withdrawal negotiations beforehand.

“The withdrawal agreement has to be negotiated before the UK can negotiate future trade deals,” he said. “Part of that will include negotiations about contiguous borders between the 27 member states and the UK. The status of Spain and Gibraltar will be part of that. If Spain blocks that, it will be much harder for the agreed negotiations to get a qualifying majority in the Council of Ministers.”