The easyJet airline has apologised to a blind woman who was prevented from boarding her flight on Sunday because her guide dog had no documentation.
Joanna Jones flew from Belfast to Gatwick last week with her dog on a different airline.
Although her dog still wore an official harness and collar tag, she was told it needed a certificate on their return.
She flew home on Monday after easyJet was contacted by the Guide Dogs Association in Belfast.
The airline transferred her to another flight on Monday.
Her fiance, Barry Toner, who also uses a guide dog, said he received a call from Ms Toner on Sunday evening saying that easyJet would not allow her onto her flight.
"She said they were asking for a certificate to prove that her dog was, in fact, a guide dog, despite the fact the dog was wearing an official guide dog harness and had the guide dog medallion on its collar," he said
"This certificate they were asking for, we simply are not given one. It's not a document that I or other guide dog owners that I spoke to online have ever heard of."
Mr Toner said he had a similar experience with easyJet last year but had eventually been allowed to board his flight.
Easyjet's corporate affairs manager Andrew McConnell said that the airline welcolmed passengers travelling with assistance dogs and carried hundreds each year.
"However, in line with CAA guidelines, easyJet's regulations make clear that documentation must be carried showing that they are a trained guide dog," he said.
"Guide dogs receive intensive training from accredited organisations to ensure that they can cope with the conditions on-board an aircraft.
"In this case, unfortunately Miss Jones did not have this documentation with her and by the time it was faxed through she missed her flight.
"EasyJet staff offered every assistance to Miss Jones and transferred her free of charge onto the first available easyJet flight this morning."
The Guide Dogs Association's transport policy officer John Welsman said the airline had adhered to flight guidlines.
"While what happened to Ms Jones is unfortunate, airlines do have rules which say that assistance dog owners must provide proof of their dog's status.
"Those rules are in place to protect passenger safety, and we would remind all our guide dog owners to carry their ID cards with them at all times."