Factbox: What next after Britain backs Heathrow expansion?

By Sarah Young LONDON (Reuters) - The British government gave Heathrow the green light on Tuesday to build a third runway, which will be the first new full-length runway since the 1940s in southeast England, the economic engine of Britain. Heathrow has said the new runway will be open for flights by 2025, but building is not expected to start until 2021, with the project subject to a parliamentary vote and years of consultation processes and planning approvals. A majority of lawmakers back expan