Ryanair have said they will base all 50 of their new planes outside of the UK because of Britain's decision to leave the EU.
Chief executive Michael O'Leary said there was "much more political certainty in continental Europe", and warned of lower growth over the next few years.
Mr O'Leary said: "We're being very cautious about the amount of capacity we're allocating to the UK over the next two or three years until we get some kind of indication of what Brexit will look like.
"It's not because we're annoyed or anything with the UK, but we have much more political certainty in continental Europe than we have in the UK while they're all running around trying to work out what Brexit looks like."
Speaking at the first PMQ's since the summer recess, Theresa May said the government would not "provide a running commentary" on the Brexit process.
She told parliament: "We will not take decisions until we are ready, we will not reveal our hand prematurely and we will not provide a running commentary on every twist and turn of the negotiation".
In May, then Chancellor of the Exchequer George Osborne joined former adversaries Ed Balls and Sir Vince Cable on the Remain campaign trail and appeared together at the Ryanair hangar at Standsted Airport.
During his speech, Mr Osborne warned of the potential risks posed by Brexit and said 450 jobs and almost £1 billion investment announced by the airline could be "at risk if we left the EU".
On Wednesday, O'Leary described politicians now working to take Britain out of the European Union as "headless chickens" with "no idea".
He said: "There's a bunch of headless chickens here, they don't know what they voted for and have no idea where they're going to finish up, so we have to be cautious with our expansion next year, which is a pity.
"None of the new aircraft we take delivery of next year will be based here in the UK and already you can see the Brexit decision is costing real jobs, real visitors are being lost and real investment is being postponed."
Despite basing future aircraft abroad, Mr O'Leary said he would expand and invest in Scotland "the following day" if the Scottish Government scraps air passenger duty.
He said the move could bring in £400m in VAT revenue as well as creating approximately 3,500 jobs.
"I'm always wary of politicians' promises, if you want to cut taxes then cut them now.
"You scrap it and we will begin the process of doubling our traffic the following day and I think we would go from five million to 10 million passengers within about two years.
"There's nothing but upside in this. I'd take my chances on Brexit simply because the prize of getting rid of £13 a passenger here is such a big one for us as an airline", he added.