If someone hacked GPS and instrument landing systems at the major airports in the greater New York City area, there would be no easy place to send arriving planes. In the best-case scenario, GPS jamming will cause significant delays as pilots are forced to reroute a flight’s last miles, costing airlines and passengers, says Martin Lauth, a former air traffic controller, who now is an associate professor of air traffic management at Florida’s Embry-Riddle Aeronautical University. Security analysts and aerospace engineers who have studied the events say the likely cause in at least some instances is malicious interference. Only the intervention of an alert air traffic controller averted catastrophe. In June a passenger aircraft landing in Idaho nearly crashed into a mountain, according to NASA’s Aviation Safety Reporting System. In incidents involving at least four major airports in recent years, approaching pilots have suddenly lost GPS guidance. In a safety advisory issued this past April, the organization wrote that aviation is now dependent on uninterrupted access to satellite positioning, navigation and timing services and that vulnerabilities and threats to these systems are increasing. That kind of scramble can cause a crew to lose control of an aircraft.

In some cases, pilots had to immediately speed up the plane and loop around the airport to try landing again. In July and August of that year, the International Civil Aviation Organization received more than 50 reports of GPS interference at the Manila airport alone. Fortunately, skies were mostly clear that day. The crew members pulled it off, but they were anxious the whole way in. Surprised, the controllers told the pilots to land the wide-body Boeing 777-300 using just their own eyes. The pilots radioed air traffic controllers and said they had lost GPS (Global Positioning System) guidance for the final eight nautical miles to “runway right-24.” On August 5, 2016, Cathay Pacific Flight 905 from Hong Kong was heading for an on-time arrival at Manila’s Ninoy Aquino International Airport when something unexpected occurred.

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