On clear or partly sunny days, people might look up at the sky and see straight lines of what appear to be clouds or white smoke. These lines are not smoke or natural clouds; they are contrails produced by aircraft. Contrails form because water vapor from jet engine exhaust passes through a cold and humid part of the air at high altitudes. Sometimes the jet that created the contrails is not visible overhead because winds aloft have blown the vapor trail into the observed area after the jet has passed. Naturally occurring high thin cirrus clouds do not form straight lines, they are more diffuse and irregular in shape than a contrail. Can an app be developed to help a ground observer determine the probability that an aircraft made the thin lines of white 'clouds' overhead?

Contrails may appear on clear or partly cloudy days because of jet engine exhaust that contains water vapor. The water vapor condenses at high altitudes where a layer of air is cold and contains moisture. The condensation is visible from the ground, appearing to look like pencil thin lines of 'cloud.' Altitudes where contrails can form from jet exhaust range from 25,000-35,000 ft, depending on the moisture content of the air layer. Two major types of contrails can be observed, those that are persistent (can last for hours or days) and those that are short-lived (appear for a few minutes before dissipating). Persistent contrails can spread over thousands of square kilometers and eventually join the high thin cirrus clouds that naturally occur. With global air traffic on the rise, climate scientists are concerned about the additional 'clouds' produced by jets. An app that can reliably tell a contrail from a natural cirrus cloud could help scientists quantify the presence of human-induced cloud cover.

The contrail app should give the approximate location of the user on the ground and the approximate location of the possible contrail above. Using flight-tracking information available from various sources in the US, the app should be able to match the location on the ground with the approximate commercial flight location. Note: This app will only use commercial air traffic data. Private or military jets are not included in this challenge. If a flight path reasonably matches the ground location, the ground observer can infer that the white lines are contrails.