The High Court was due to rule on the legality of the mass walkout planned by the airline's crews between December 22 and January 2, amid a deepening row over working conditions.

Last-ditch talks between BA executives and union bosses were meanwhile set to resume a bid to secure a deal and avoid disrupting the travel plans of passengers who had purchased tickets on the airline to visit friends and family over the Christmas and New Year holidays.

Prime Minister Gordon Brown on Wednesday urged both sides to resolve the dispute, saying he was "very worried" about the threatened strike.

"We are agreed that the different sides in this dispute have got to look outwards and not inwards, they have got to think of the passengers that they serve, they have got to think about the future of their company," Brown said.

Unite union joint leader Tony Woodley said that although members wanted to avoid a strike, there would be no backing down over demands.

"We don't want a dispute and neither do our members, but we are not prepared to see major changes to terms and conditions imposed on our members."

Cabin crew voted this week overwhelmingly to go on strike over job cuts, conditions and pay, a move that BA chief executive Willie Walsh described as "senseless", while also vowing to stand firm over the job cuts.

BA launched the legal action in a bid to prevent the strike by 12 500 cabin crew members. It argued that Unite balloted workers who had already accepted voluntary redundancy, which they claim renders the overall vote invalid.

BA lawyer Bruce Carr told the High Court on Wednesday that the consequences of a strike for the airline over Christmas would be "financially disastrous".

Judge Laura Cox will continue hearing the case before likely making a decision in the afternoon.

The industrial action comes at a critical point for loss-making British Airways, which is slashing costs and attempting to merge with Spanish carrier Iberia in a desperate fight to stay competitive.

Travellers meanwhile faced fresh headaches after some baggage handlers at Heathrow Airport announced they were set to go on strike next week in a row over pay.

Unite said on Wednesday workers at Heathrow and Aberdeen will take action from December 22, with further walkouts planned on Boxing Day and January 3.

Eurostar train drivers and onboard staff are also set to walk out on Friday for 48 hours, union officials said, threatening disruption to services between London, Paris and Brussels.

If you're flying with British Airways over this period, your flight may well be cancelled or rescheduled. The airline says it is adjusting flight schedules, and that customers should ensure their contact details are correct, by updating the 'Manage my Booking' service on ba.com. You can also Click here for more info on changing your booking.

Ed's note: The strike action will not affect domestic and regional flights operated by the franchisee BA/Comair. Only international flights operated by British Airways (i.e. to London and beyond) will be affected.