Wake Turbulence

Best avoided, especially if generated by a Boeing 757 or Airbus A380, the two types of aircraft whose wake is particularly vicious to aircraft below.

Usually invisible, the wake descends at 500 feet-per-minute, so pilots have to imagine where they are. Here the atmosphere is moisture-laden so that contrails have formed, making the wake visible.

On head-to-head airways in RVSM airspace, (1,000 feet vertical separation), when an aircraft passes directly overhead pilots will check their wind readout and determine where the descending wake will be in two minutes, and manoeuvre their aircraft to avoid it.

Strategic Lateral Offset Procedures (SLOP) allow Pilots in Oceanic Airspace to offset to the right, up to one or two nautical miles without having to advise ATC. When piloting an A380 it's wise to put yourself on the most downwind SLOP track to make it easier on other crews.