This is one of the first questions I can remember my son asking me which took me by surprise. At age 3 he was and is still (approaching 5) fascinated by planes and other flying machines such as airships and hot air balloons. I never really thought about the smoke trail and assumed that it was engine smoke. Not quite as I found out.
WHY DO PLANES LEAVE SMOKE TRAILS: First I learned this in a children’s picture book about airplanes (I Love Planes by Sturges or Airplanes by Barton), which referred to these marks as sky scratches. These marks in the sky are basically water droplets frozen by the high altitude. It is true that these water droplets are created by the exhaust system of the plane much like your car produces water (the drips out of the exhaust pipe after driving) but the sky scratches are not smoke, more like frozen steam. For more technical information see contrails and vapor trails in Wikipedia.
SO THEN, WHAT IS SKY WRITING: Now that’s smoke- used by smaller aircrafts to create a message in the sky. Smoke is also used in air shows by the trick planes for dramatic effect. Often several planes will create the same message with one flyby, this type is created using bursts of smoke set to release at precise times.
OTHER INTERESTING PLANE FACTS: Commercial airplanes usually fly at speeds of 550-575 miles per hour. The Concorde, when operational, flew over twice as fast at 1,350 m.p.h. The fastest plane on record at the turn of the century was the Lockheed SR-71 Blackbird which flies at Mach 3 (Mach is the speed of sound which is 758 m.p.h.) or 2,274 m.p.h. and yes it has a pilot. NASA has designed a plane to travel at speeds nearing Mach 10 (that’s 7,580 m.p.h.) called the X-43A Scramjet which is part of the Hypersonic or Hyper-X. In 2004 the X-43a was clocked at 7,000 m.p.h. which is the current world record. Now if they can only get the planes to leave on time. For great information on more aircraft visit the Smithsonian Air and Space Museum via the web or in Washington D.C. — it will not disappoint.
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