According to Reuters, a British vote to leave the European Union would call into question EU agreements on open airspace, creating uncertainty for both UK and EU airlines.
Flying rights between two countries, including how many airports a carrier may fly to and how often, are typically negotiated in bilateral treaties. By creating the single aviation market in the 1990s, the EU allowed the region´s airlines unlimited access to the skies of fellow member states, doubling traffic growth in the four years after liberalisation.
Liberalisation means an Irish carrier can fly between Britain and Spain, or a British carrier can operate domestic flights within France, opportunities seized upon by low cost carriers.
A Brexit vote in the British referendum on EU membership would affect all pan-European carriers, not just British ones. US routes could also be affected. Britain´s airlines enjoy unlimited flying rights to the US, including on trans-Atlantic routes, thanks to the EU-US Open Skies agreement. Britain could either negotiate joining the Open Skies deal, or seek its own bilateral agreement with the US.