Always useful to give some context - this is what he really said:
"“The sensible outcome here is to ignore the plebiscite of 12 months ago, stay in Europe and continue to benefit from Open Skies.”
This as he gave a EU Parliament committee in a session titled "Brexit in aviation: Perspective of the Airlines and Tourism Industry" his views on the effects of Brexit. The session was also attended by Willie Walsh (somewhat more optimistic) and top brass from Airbus (concerned about moving staff and components), TUI (pretty much echoing O'Leary), Lufthansa (blabbering about the ME and missing the point) and Airlines of America (warning of the consequences for the TATL JV).
Some quotes from what MOL said:
"This is going to be a real mess. Brexit will be one of the great economic suicide notes in history."
"There is not a legal mechanism on which airlines can operate in a 'hard Brexit, no deal' outcome. There will simply be no flights"
“There is a real prospect, and we need to deal with this, that there are going to be no flights between the UK and Europe for a period of weeks, months beyond March 2019."
““There is not going to be an interim agreement, there is not going to be a legal basis, we will be cancelling flights. We will be cancelling people’s holidays for summer of 2019.”
"I am not sure the Brits, who like their holidays in spain fancy Karachi" (talking about a remark by a senior Brexit minister who had allegedly told him the lost European airline traffic could be made up through a bilateral agreement with Pakistan)
“By September 2018 when your average British voter is sitting down to work out where he is going on his holidays in 2019, the two options he will have are to drive to Scotland or get a ferry to Ireland”