British Airways cabin crews will strike over Christmas, their union said Monday.

A walkout would disrupt travel for thousands of travellers during one of the busiest travel periods. Aviation analysts have suggested one million British Airways passengers could be affected worldwide.

British Airways cabin crews could go on strike Dec. 22. (CBC)

Len McCluskey, the assistant general secretary for Britain's Unite union, said the strike would begin Dec. 22 and run for 12 days, until Jan. 2.

The airline operates 10 daily flights daily between Canada and London's Heathrow Airport, including service between Toronto, Montreal, Vancouver and Calgary. A 12-day strike could disrupt the plans of more than 20,000 passengers on Canadian routes.

Union members voted by a margin of 92.5 per cent in favour of the action.

'You don't often get ballot results like this unless there is a deep-rooted sense of anxiety, concern and anger.' — Len McCluskey, Unite union

"You don't often get ballot results like this unless there is a deep-rooted sense of anxiety, concern and anger," McCluskey said at a news conference.

British Airways lost $346 million US in the six months ending in September because of falling demand and has cut costs by eliminating 1,700 jobs, freezing pay for current staff and offering lower wages for new employees.

CEO Willie Walsh called the strike "completely unjustified" and said that union misled members about over the necessity and fairness of the airline's new pay and work proposals.

He said the company is "working hard on contingency plans, and will announce them as soon as they are finalized."

The airline also revealed on Monday that its pension deficit has grown to more than $6 billion and said it would consult with employees about a recovery plan.

With files by The Associated Press