Digital security weaknesses in U.S. air traffic control systems as simple as using unencrypted networks enable attacks from terrorists and foreign nations that could prevent the safe landing of more than 7,000 commercial passenger and cargo flights.

The national airspace system, the Federal Aviation Administration network that guides the country’s airplanes and includes air traffic control systems, is dangerously open to outside attacks because of lax cybersecurity, according to a Government Accountability report.