Journal

When a city moves its airport, the old one becomes a park, a housing estate or a cruise terminal. The runway is usually the last thing to go.

The longest runways were not built for airliners. They were built for thin air, for test flights, and for a spacecraft that landed without engines and could not go around.

Some airports publish runways that are really lanes of water, marked on a chart, bounded by buoys, and closed to heavy aircraft when the lake begins to freeze.

The oldest airports were fields where someone first put an aeroplane down. A few never stopped being airfields, and each of them counts its age in its own way.

Above 4,000 m an airliner needs a longer runway, a lighter load and, in some cabins, oxygen for the passengers. A few airports live with that every day.

A few airfields sit below mean sea level — on the shore of the Dead Sea, in Death Valley, on the floor of a drained Dutch lake. Below zero, the altimeter simply reads negative.

Above the 76th parallel, a handful of airfields still take flights you can book. Most have gravel runways, weekly flights and months without sunrise; the busiest is built on ice-rich permafrost.

Between Westray and Papa Westray in Orkney, an eight-seat Islander covers 2.7 km in about a minute and a half. It is the shortest scheduled flight in the world — and a lifeline, not a stunt.

Most runways are built as flat as the ground allows. A few slope on purpose — aircraft land up the hill and take off down it, and there is only one way to do either.

Airports are renamed after presidents, composers and footballers — sometimes within weeks of a death, sometimes two centuries after it. The three letters on the baggage tag almost never change.