In the late 1990s, airline companies began to fly polar routes between North America and Asia in order to avoid strong wintertime headwinds and thus to reduce travel time
Decreased travel time makes it possible to carry less fuel, thus saving costs, and allows the airlines to transport more passengers and cargo, increasing revenues.
Because of the clear economic benefits, the use of polar routes has grown dramatically over the last decade. In 2007, thirteen carriers flew polar routes for a combined total of almost 7300 polar flights,
an increase of nearly 2000 flights from the prior year.
The transpolar routes take aircraft to latitudes where satellite communication cannot be used, and flight crews must rely instead on high-frequency (HF) radio to maintain communication with the airline company and air traffic control, as required by federal regulation.
During certain severe space weather events (referred to by the SWPC as "solar radiation storms"), solar energetic particles primarily protons accelerated by CME-driven shocks—spiral down geomagnetic field lines into the polar ionosphere, where they increase the density of the ionized gas, which in turn affects the ability of the radio waves to propagate and can result in a complete radio blackout.
Such polar cap absorption (PCA) events can last for several days, during which time aircraft must be diverted to latitudes where satellite communication links can be used. During several days of disturbed space weather in January 2005, for example, 26 United Airlines flights were diverted to nonpolar or less-than-optimum polar routes to avoid the risk of HF radio blackouts during PCA events. The increased flight time and extra landings and take-offs required by such route changes increased fuel consumption and raised cost, while the delays disrupted connections to other flights.
Reference : The National Academies, "Severe Space Weather Events-Understanding Societal and Economic Impacts: A Workshop Report - Extended Summary", pp7-8, 2009