Heathrow Airport’s $83.6 billion third runway was always going to be expensive

After two decades of dithering and about-turns, Britain is finally moving ahead with

plans for a third runway at London’s Heathrow Airport

. Look at the usage data, and it is hard to doubt the economic case for expansion: Europe’s busiest airport carries far more passengers relative to its size or number of runways than rival hubs.

Yet, the proposal has already turned into a dogfight between airlines and the airport’s owners over costs. Given Britain’s chequered record with infrastructure mega-projects, anxieties are justified.