Unite union is refusing to back the British Airways (BA) Iberia merger unless jobs and standards are guaranteed.
Unite national officer for civil aviation Steve Turner said the union, which represents BA cabin crew, has written to chief executive Willie Walsh over fears that the merger will lead to significant job losses.
It is also demanding guarantees from the airline that core UK-based services including customer service, engineering, maintenance and cabin crew are protected.
The union also wants assurances that BA’s standards of service will be maintained and Heathrow will remain the airline’s hub, supported by Gatwick.
Turner said: “We need assurances from the outset from BA and Iberia that compulsory redundancies will be avoided and that the new airline will be the best in the business in terms of passenger service.
“It is imperative that both companies sit down as soon as possible with the unions here and in Spain to discuss how jobs and standards can be safeguarded.
“Our continued support for this project, as well as the stability we are all seeking to bring to British Airways at this current time, are dependent upon a satisfactory agreement being reached between us and both companies.”