British Airways passengers need not fear strike action for at least another day after senior judges said they will not decide before Thursday whether a walkout by the airline staff will be illegal.

Unite, the trade union that represents more than 90% of BA cabin crew, was furious on Monday after a high court judge ruled 20 days of planned strikes unlawful. Unite said Mr Justice McCombe's decision was "an absolute disgrace" which ranked as "a landmark attack on free trade unionism" and lodged an appeal this at the Royal Courts of Justice.

In recognition of the case's wide-reaching implications, the lord chief justice, Lord Judge, chaired a three-strong panel, sitting with the master of the rolls, Lord Neuberger, and Lady Justice Smith, to decide whether to overturn the judgment. The judges, however, delayed their decision until 9.30am Thursday.

If the appeal court upholds the BA injunction the airline does not expect to restore a full service until the end of the week. In the meantime, it says, it will fly seven in 10 passengers to their destinations, or about 60,000 people a day.

If Unite wins the appeal the strike could be back on as soon as midnight .

The original union plan was for strikes from 18-22 May, 24-28 May, 30 May-3 June, and 5-9 June. Eighty-one percent of BA staff voted for the industrial action.

BA won the original injunction on the grounds that Unite had breached a clause in the 1992 Trade Union Act which says unions must not only tell all eligible voters of the ballot result but include a breakdown of votes, including spoiled ballots. The airline successfully argued that the union had failed to provide all the necessary information in an easily accessible place, particularly the nugget that 11 of the 9,282 ballots cast had been spoiled.

But , Lady Justice Smith said: "In this case, the numbers [of spoiled papers] are so small that they can't be of interest to anybody." After BA's barrister, David Reade QC, suggested Unite had made it too hard for members to access the ballot's full results, Lord Judge said that, given BA staff had twice voted overwhelmingly for strike action, they would surely have gone out of their way to get the result. "Are we really to assume the members of the union weren't absolutely riveted by the prospect of the ballot and the result?"

The judge asked whether the implication of the strike ban could be that any firm could stop a walkout if the workforce did not comply with section 231 of the Act. "Is this the way labour relations are going?"

Tony Woodley, joint leader of Unite, tonight insisted the union had abided by the rules, doing everything "humanly possible" in an online ballot of BA cabin crew about an offer concerning the disputes.

www.guardian.co.uk

19 May 2010