Commercial Flights Are Experiencing ‘Unthinkable’ GPS Attacks and Nobody Knows What to Do::New “spoofing” attacks resulting in total navigation failure have been occurring above the Middle East for months, which is “highly significant” for airline safety.
Turns out it’s 1000 knots (~600m/s), or 18,000 feet. So it’s the altitude in this case. But a slow-moving drone at <18,000ft is fine.