Common sense will prevail to keep airlines flying after Brexit, a European airlines chief told its annual conference in Edinburgh today.
Montserrat Barriga, director general of the European Regional Airlines Association (ERA), said she was optimistic about the outcome.
However, her remarks coincided with the head of the Whitehall spending watchdog warning MPs that flights to Europe could be grounded in the event of an "unfriendly" Brexit.
Ms Barriga said: "We often hear 'common sense will prevail'.
"I personally think people's and companies' needs will prevail and there will be a positive agreement.
"I am optimistic, but still realistic."
The association represents 50 airlines, including Loganair, Flybmi and Flybe, which fly 74 million passengers a year on 1,800 routes in a European industry that employ 300,000 people.
Ms Barriga also warned the ERA general assembly at the Edinburgh International Conference Centre it would have to lobby hard to achieve that Brexit outcome next March.
She said: "European citizens need an open and unrestricted bilateral agreement between the EU and the UK.
"An early and favourable resolution of Brexit negotiations is urgently needed.
"The EU and the UK need to be far more transparent.
"Do we really think there will be aircraft grounded because of the lack of a political agreement?
"Brexit is a European problem that needs agreement for aviation before the UK formally leaves the EU - not just the day before it leaves the EU.
"We need a comprehensive agreement that includes traffic rights, pilot licences, security agreements, leasing conditions that hopefully mirrors today's situation as much as possible."
But Sir Amyas Morse, the head of the National Audit Office, rejected claims it was "implausible" to suggest flights could be halted after 29 March, saying a breakdown could happen by "mistake" as well as by the result of deliberate action.
He told the Commons EU committee that if the UK was to refuse to pay the £39 billion "divorce" settlement in the event of a no-deal Brexit, it could lead to Brussels adopting a similarly tough line.
"It is not implausible. It is not impossible. It could happen by mistake rather than deliberately. It depends upon how friendly or unfriendly the accompanying music is as all this goes on," he said.
"If you say, 'Well, we're leaving in March and PS, we're going to take a very tough attitude, you can take us to court for whatever money you want from us and, and, and ...' it is not impossible to think of scenarios where people might not be terribly helpfully disposed to us.
Aviation consultant John Strickland underlined at the ERA conference that the situation was far from clear.
He said: "There is less than six months to go and we do not know where the heck we are going."
But he added: "I cannot see it is in anyone's interest for things to come to a grinding halt - nobody wins."