Blame COVID-19 travel restrictions or Brexit but whatever the cause, some British citizens trying to return to their homes in Spain have been barred from boarding flights.
Airlines are refusing documents that before Brexit had been valid proof of a Brit's status as a resident of Spain.
Their ordeal comes amid heightened travel restrictions over a coronavirus variant that has been blamed for faster spread in the UK and highlights the bureaucratic complexities resulting from Britain's departure from European Union.
Both Spanish and British authorities said on Sunday that the certificate of EU citizenship with a foreign national identification number issued by Spain is still valid for British citizens residing in Spain under the bilateral provisions that followed the UK's withdrawal from the bloc on December 31.
But the travellers say British Airways and Iberia have been refusing to let them board for the past two days. The airlines, part of the IAG group, didn't immediately respond to requests Sunday for comment from The Associated Press.
Around 300,000 British citizens are registered as permanent residents in Spain, although before Brexit, many more had been living full or part-time in the country without officially registering.
Patricia Moody, a 69-year-old retiree who has called the southern Spanish town of Zurgena home for nearly four years, was among at least nine people unable to board a Madrid-bound flight from London's Heathrow Airport on Saturday.
Moody said she and her husband, who she says needs to see his doctor back in Spain, have spent 1900 pounds ($A3,377) on getting tested for the virus, travelling to the airport and booking new tickets after they were refused boarding. Their second attempt was also futile.
"Throughout all the months of negotiating Brexit, we were always assured that nothing would change for us," she said.
"It's horrendous and we are suffering because of their incompetence."