It shouldn't be a decision between expanding either Gatwick or Heathrow but both, a spokeswoman for the Association of British Travel Agents said.
Victoria Bacon told ITV News: "By the time this additional runway gets built in 2025 there will be a need for more capacity so planning right now for the long term is really important. We don't think it's either or, it's both."
Tory MPs are taking lumps out of each other on Heathrow, grammar schools and - above all - the true meaning of Brexit.
Environmentalist Goldsmith called the move "catastrophic" - and announced he will now stand as an independent in protest.
The expansion of the London airport will affect the whole of the UK, with more domestic routes, while impacting air fares and house prices.