London — The sudden, full-day closure of London's Heathrow Airport on Friday caused by a fire in a nearby electrical substation threw the travel plans of an estimated 200,000 people into disarray.

A map of the proposed third runway at Heathrow reveals how expanding the west London airport will impact surrounding areas. Heathrow has announced a multi-billion-pound investment to enable the plans.

London's Heathrow Airport reopened on Saturday after a power outage at one of the world's busiest airports the previous day caused widespread chaos and cancellations. A post on the airport's website ...