2010 California contrail incident

On the evening of Monday, November 8, 2010, an unusually conspicuous contrail appeared about 35 miles (56 km) west of Los Angeles, California, in the vicinity of Catalina Island. News footage of the event from a KCBS helicopter led to intense media coverage and speculation about a potential military missile launch, with many reporters and experts discussing the vapor trail and theorizing about its source.

Coverage continued for several days. The Pentagon released a statement on November 9 that it could not identify the source of the vapor trail, but both the North American Aerospace Defense Command (NORAD) and U.S. Northern Command stated that it was not a foreign military launch. On November 9, the FAA also issued a statement that it had not approved any commercial space launches in the area for the prior day. On November 10, some 30 hours after the "mystery missile" first gained press attention, a Pentagon spokesman stated there was "no evidence to suggest" that the plume was anything but an aircraft contrail. Some experts, however, held that the vapor trail could not be conclusively identified as an aircraft contrail, and others stated it was a missile.

Although some question persisted about the vapor trail's origin, the incident came to be seen as an example of news outlets being "captives of their sources" and irresponsibly pushing unverified theses; it was also interpreted as a lesson in the importance of exploring alternative hypotheses that fit available data. U.S. federal and military authorities also faced criticism for what were described as "inconclusive" answers and for allowing the issue, in the words of one commentator, to "fester for days" without a clear resolution.

Background

Contrails, short for "condensation trails," are linear cloud formations produced by aircraft exhaust, air pressure changes, or rocket emissions, usually at commercial cruising altitudes several miles above the ground.