British Airways (BA) has warned union Unite that it intends to return to the courts in a bid to have the strike action ruled unlawful.
BA has written to Unite "to remind them to retain all relevant paperwork," said a BA spokeswoman.
The airline stressed it is not appealing the court's decision last week, when an injunction against Unite was overturned, but intends to continue with a full hearing on the legality of the strikes.
"The union would have been fully aware that the point of law over the strike ballot result would come to a full court case in due course," said BA.
Meanwhile, Unite continues with the BA cabin crew strike, saying the "holding strong with crew determined to end the intimidation by the company as they fight to save their jobs".
Unite estimated the strike has cost BA £70 million so far and could cost as much as £152 million as passengers switch to other airlines during the peak summer season.
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