Ever been looking out the window of a plane and seen another one flying past in the sky and wondered exactly how close it is? It’s actually probably not as close as you think.
Laws governing the allowable distance between aircraft in the skies differ slightly around the world but in the majority of situations planes that are at the same altitude are kept at a distance of 5 miles from each other. You can usually see a plane that is 5 miles away so it wouldn’t be unusual to see a plane at the same level as you.
In terms of separating aircraft vertically, planes fly at levels spaced a 1,000 feet apart – if you’ve ever flown into somewhere where you’ve had to take up a holding pattern (London Heathrow being a classic example) then you may have seen aircraft either above or below you. These are always at least 1,000 feet vertically separated from you.
To safegaurd planes accidentally getting too close to each other, all commercial aircraft are fitted with a system called a Traffic Collision Avoidance System (TCAS). This system allows aircraft to see where each other are and if two aircraft get too close to each other the TCAS systems in each aircraft “talk” to each other and issue avoiding actions to the pilots.