Ryanair has triggered contingency plans to restrict the voting rights of British shareholders if it leaves the European Union without a deal on future relations or quits both the EU customs union and single market in a "hard" Brexit scenario.
Ryanair said last year it would have to restrict the rights if UK shareholders ceased to qualify as European Union nationals to ensure it remained majority EU-owned to comply with its licensing and flight rights.
Its board passed a number of resolutions on Friday which will become effective on the date British nationals become non-EU nationals, the airline said in a statement.
At that point, shareholders will be issued with restricted share notices.
They will specify that the shareholders will not be entitled to attend, speak or vote at any general meeting of the company for as long as those shares are treated as restricted shares.
"These resolutions will remain in place until the board determines that the ownership and control of the company is no longer such that there is any risk to the airline licences held by the company's subsidiaries pursuant to EU Regulation 1008/2008," Ryanair said.
Ryanair's chief financial officer Neil Sorohan said last month that while the airline was 55% EU-owned, Britain-based shareholders controlled 20% of its stock.
He told Reuters he expected half of those to redomicile to the EU in a no-deal or "hard" Brexit.
Chief executive Michael O'Leary also said last month that the company might look to buy back shares in the event of a no-deal Brexit to use it as an opportunity for British shareholders to dispose stock due to the planned restrictions.
Meanwhile, Ryanair shares fell in Dublin trade today amid growing concerns about possible disruption from UK's exit from EU, traders said.
Traders said the drop was not related to the crash of Boeing's 737 MAX 8 passenger jet operated by Ethiopian Airlines yesterday.
Ryanair is one of the US planemaker's biggest customers.
The airline is due to take 50 modified 737 MAX 8s, dubbed the 737 MAX 200, this year.
The aircraft accounts for its entire fleet renewal plans and is due to make up 10% of its fleet by the summer of 2020.