International airlines are worried the British government is not moving quickly enough to address the impact of Brexit on aviation and passengers. The UK’s departure from the European Single Market will also see it leave the European Common Aviation Area and has raised questions about Britain's international air services agreements. While the Brexit deadline is March, 2019, International Air Transport Association director general Alexandre de Juniac warned Wednesday that the aviation deadline was earlier. The clock was ticking, de Juniac told the UK Aviation Club, and time was precious. “Normally passengers can book travel about a year in advance,’’ he said. “At a minimum, the flight schedules and seat and cargo inventories must be available at least six months in advance. “So that puts the airlines’ deadline at October, 2018—just 11 months from now.’’ The IATA boss argued the UK’s post-Brexit prosperity would depend on the strength of its connectivity with Europe and the rest of the world. He said the departure of Britain from the European Union would see air traffic rights to the UK  associated with Europe thrown into question. “The basis of international aviation is bilateral air services agreements,’’ he said. “There is no WTO agreement to fall back on. For that reason, I don’t see any alternative to a negotiated agreement." Airlines have made no bones about the fact they are disappointed with the Brexit decision or  that it will make life more difficult for them. De Juniac predicts that finding a solution would be difficult and is pushing for an early resolution of the issues. Some of the issues about which IATA is concerned include  change in customs procedures that could see the number of transactions balloon from 4.6 million a month to 21 million, whether EU nationals will have access to automated border kiosks and the UK’s relationship with European Aviation Safety Agency. De Juniac said passenger numbers would grow regardless of Brexit and solutions needed to be found quickly. “My message to all involved is three-fold: get started, don’t step backwards and don’t underestimate the work ahead,” he said. The IATA boss also addressed ongoing arguments about a third runway at London's Heathrow Airport  as part of a call on the UK government to address severe capacity constraints in the UK’s south-east. The Department of Transport recently re-opened public consultation on the planned third runway after publishing a series of new reports on noise and air quality. "Heathrow is where expansion should take place,’’ de Juniac said. “I know the struggle to build a third runway has meant decades of frustration. But the UK will be left behind in the globally connected world if it does not come to a final decision and implement it."