An event last year at Newark Liberty International Airport in New Jersey showed that it only takes one jammer to cause disruption. Airport controllers had installed a new GPS-based landing system, so that aircraft could approach in bad visibility. But it was shutting itself down once or twice a day. It took several months to find the culprit: a driver on the nearby New Jersey Turnpike using a portable GPS jammer to avoid paying the highway toll. This trucker was cruising past twice a day, crippling an airport as he went.