There's a warning 140,000 jobs are at risk unless Heathrow expands. The GMB and Unite unions, supported by the Institute of Directors say tourism, exports and foreign investment will also be hit over the next decade if a third runway is not built.
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Union members will hold rallies across the UK as part of the strike action over a rejected 1.1% pay offer.
Wednesday morning's weather for the east of the region
Wednesday morning's weather for the west of the region