4B70.20 Airplane Vapour Cones (Picture)


Adiabatic cooling, condensation


This is simply a picture of a jet fighter travelling close to the speed of sound. The combination of the shape and speed of the airplane produces zones in which the pressure and temperature are reduced below the dew point, causing water vapour to condense out of the air. This produces the vapour cone seen in the picture, in addition to the condensation just behind the cockpit.

This is a photograph from the US Department of Defense, July 1999. Thanks for their permission to reproduce the photo here. The photo is described as follows:

The Sight of Sound

Navy Lt. Ron Candiloro's F/A-18 Hornet creates a shock wave as he breaks the sound barrier July 7. The shock wave is visible as a large cloud of condensation formed by the cooling of the air. A smaller shock wave can be seen forming on top of the canopy.

It is possible for a skilled pilot to work the plane's throttle to move the shock wave forward or aft.

Candiloro is assigned to Fighter Squadron 151, currently deployed with the USS Constellation battle group.

(U.S. Navy photo by Ensign John Gay)



  • [1] Jet picture


This is simply a show-and-tell demo about this thermodynamic phenomenon.


Additional Resources


  • PIRA 4B70.20


  • Don't attempt this jet fighter maneuvre at home!

Last revised

  • 2020


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If you have any questions about the demos or notes you would like to add to this page, contact Ricky Chu at ricky_chu AT sfu DOT ca.