Low-budget carrier EasyJet has started suspending voting rights for some shares still held by non-EU interests, in order to comply with EU ownership regulations.
EasyJet holds an EU operating license and, therefore, must be majority owned by the EU and the citizens of the countries concerned.
But EasyJet's shareholder structure on January 1, when the new UK-EU trade deal went into effect, showed non-EU holdings to stand at 52.65% - above the limit of 49.5% of the enterprise.
EasyJet said it had activated the emergency plan and "launched measures to suspend voting rights" on certain shares held by non-European interests.
He said this involved sending "affected share notices" to the affected shareholders, and said shares recently acquired by those shareholders would be suspended in advance.
Similar actions have been taken by Wizz Air and Ryanair.
Affected EasyJet shareholders will not be permitted to attend, speak or vote at company general meetings.
EasyJet also warned that if non-European holdings continue to exceed a maximum of 49.5% over a continuous period, this will "force" the affected shareholders to sell their shares to EU nationals.
"There is no guarantee when, or if, [the maximum allowed limit] will be removed," he added.
EasyJet has acknowledged that the new UK-EU deal does not include any reduction in airline ownership and control requirements, although clauses indicate that discussions will take place on a possible joint liberalization of ownership conditions.