Airports are warning of a potential catastrophic slump in air travel from the UK due to Brexit unless an interim aviation agreement is reached with the EU by October 2018. Gatwick, Heathrow, London City, Manchester and Stansted have submitted a confidential report to the government arguing that traffic will start to fall as early as next March. The report, written by consultancy WPI Economics and seen by Sky News, claims that passenger numbers travelling between the UK and EU countries could slump 41% in the year between March 2018 and March 2019. The report, ‘Brexit and the aviation industry: the opportunity for certainty’, said that without an interim deal, there could be 20% fewer flights from next March. “With airlines, passengers and airports having to plan months if not years in advance, this has potentially detrimental consequences for UK competitiveness, trade, growth and living standards, which all become more significant the longer that UK and EU negotiators fail to deliver a new trading relationship or transitional deal,” the WPI report says. “Although an 11th-hour deal may prevent planes from being grounded, damage to the aviation industry and the wider economy would have already been done.” A Government spokesman told Sky News: “Aviation is absolutely crucial to the UK’s economy and we are committed to getting the right deal for Britain. “Our aviation industry is the largest in Europe, and both we and the EU benefit from the connectivity it provides. “That’s why we are pursuing liberal access to European aviation markets – including all the benefits that brings for consumers.”