According to the NTSB’s Preliminary Report [PDF], the crew, alongside several other aircraft, experienced issues with their navigation system consistent with the effects of GPS jamming, as reported by Wired. This raises urgent questions about GPS jamming as reported incidents of GPS interference mount across the world. Around five minutes after this radio communication, ATC called the military and asked them to stop their GPS jamming activities in the meantime. Even though GPS jamming might sound alarming, pilots have been flying around the world for decades, even before it came into widespread use. The military’s GPS jamming exercise didn’t directly cause the crash, but it was likely the first event in the “Swiss cheese” model that ultimately caused the accident.