A contrail from an airplane flying towards the observer can appear to be generated by an object moving vertically. On 8 November 2010 in the US state of California, a contrail of this type gained media attention as a "mystery missile" that could not be explained by U.S. military and aviation authorities, and its explanation as a contrail took more than 24 hours to become accepted by U.S. media and military institutions. Distrails Where an aircraft passes through a cloud, it can disperse the cloud in its path. This is known as a distrail (short for "dissipation trail"). The plane's warm engine exhaust and enhanced vertical mixing in the aircraft's wake can cause existing cloud droplets to evaporate. If the cloud is sufficiently thin, such processes can yield a cloud-free corridor in an otherwise solid cloud layer. An early satellite observation of distrails that most likely were elongated, aircraft-induced fallstreak holes appeared in Corfidi and Brandli (1986). Clouds form when invisible water vapor ( in gas phase) condenses into microscopic water droplets ( in liquid phase) or into microscopic ice crystals ( in solid phase). This may happen when air with a high proportion of gaseous water cools. A distrail forms when the heat of engine exhaust evaporates the liquid water droplets in a cloud, turning them back into invisible, gaseous water vapor. Distrails also may arise as a result of enhanced mixing (entrainment of) drier air immediately above or below a thin cloud layer following passage of an aircraft through the cloud, as shown in the second image below: Gallery See also Chemtrail conspiracy theory Cirrus cloud Cloud chamber – particle detector that works on similar principle Environmental impact of aviation Fallstreak hole Global dimming Ship tracks Skywriting Space jellyfish Twomey effect References External links Contrail Education (archived) | NASA Contrails.nl: Contrails and AviationSmog | Galleys of contrails and aviation smog Contral Science | Reference site for debunking weird stories about contrails Aviation meteorology Cloud types Cirrus Cloud and fog physics Climate forcing