If BA has to pay in a lot more cash, Iberia could opt out of the merger.

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BA, appear resigned to having to pay more to operate there.

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The union said there was a turnout of 71% of the cabin crew it represents, and 81% voted against BA's offer last week, which sought to resolve the dispute over pay and working conditions.

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But BA may be required to give up landing slots at Heathrow, a price it has been unwilling to pay in the past.

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