Ryanair boss Michael O'Leary has warned of a "real and distinct" threat that flights from the UK to the European Union could be grounded from April 2019, meaning there will be "no holidays" that summer.
O'Leary, who has this morning handed transport secretary Chris Grayling a briefing note outlining his fears, said the aviation industry had a hard deadline of September 2018 for the agreement to be reached.
"Otherwise we will have to start cancelling flights, or taking them off sale," he said this morning.
That would leave Brits forced to get ferries for holidays to Ireland or continental Europe, O'Leary explained, saying they would be "full of Irish and British refugees".
"September 2018 is when we will start seeing the shit hitting the fan," O'Leary added.
He insisted Ryanair would be able to navigate a possible summer of chaos by deploying its 70 UK-based aircraft in intra-European flights, but said EasyJet and British Airways would have no such fallback.
O'Leary declined to comment on the details of this morning's meeting with Grayling beyond what was in the briefing document, which said it was "highly unlikely" that the UK would be able to negotiate an open skies agreement in time, particularly in light of "a distinct and noticeable lobbying effort by French and German airlines".
"The obvious consequence of any such cessation of all flights between the UK and European Union for a period of time from the end of March 2019 would be deeply damaging for UK tourism, traffic and tens of thousands of jobs at UK airports, within British tourism and the UK economy for as long as such catastrophic disruption would persist," the document said.
O'Leary said he had circulated it to the UK government after seeing briefing documents with the logos of airlines including Lufthansa, Air France, TAP, Croatia Airlines and SAS.
These groups were arguing the case for EU27 to agree terms "so onerous" that the UK would be unable to accept them without rowing back on certain "red lines", such as ECJ jurisdiction, O'Leary said.