Contrails, Condensation Vapour Trails

A contrail from an aeroplane flying towards the observer can appear to be generated by an object moving vertically. On November 8, 2010 in California, U.S., a contrail of this type gained wide 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
Distrail is short for "dissipation trail". Where an aircraft passes through a cloud, it can clear a path through it; this is known as a distrail. Because the plane's contrail is not yet visible (contrails usually form above 8,000 meters/26,000 feet, depending on the temperature and other factors) a distrail looks like a tunnel through the cloud if the cloud is very thin.