Solar flares can drown out GPS signals with potentially serious consequences for airlines, emergency services, and anyone relying on satellite navigation.

It turns out these bursts of charged particles, which produce auroras and geomagnetic storms, also generate radio waves in the 1.2 and 1.6-gigahertz bands used by GPS.

How was such a clash missed? Because GPS receivers only became common during a period of low solar activity. By 2011 solar flares will reach the peak of their cycle and receivers will likely fail. Or so Alessandro Cerruti of Cornell University, New York, told a meeting of the Institute of Navigation in Fort Worth, Texas, last week. The only solution would be to redesign GPS receivers or satellites, which may not be practical, says Cerruti.