I know LHR has some of the longest runways at about 4km, but as there is waste ground on the end of 27R, why not extend by an additional 1km+ each end?
With a 7km+ long runway you could have simultaneous arrivals and departures, if the departures line-up from the mid point.
Bet no-one has thought of that... yet.
Last edited by scifi; 11th Oct 2016 at 10:49.