Mark Harris, writing for IEEE Spectrum, has come out with a chilling report about how military testing is leading to confusion among pilots — and sometimes putting them in danger. The piece goes into why the US military is jamming GPS in American airspace and recounts some of the times it’s almost gotten civilians killed. If you’re a frequent flyer or are interested in when military testing bleeds into everyday life, it’s well worth the read.

The military is carrying out the testing, ironically, to help develop technology to counteract GPS jamming. To be fair, it’s an understandable goal, as the article details the troubles that pilots face when a technology they heavily rely on goes away. But when that happens, the pilot at least has visual cues and other instruments. The article also goes into how, instead of completely cutting out the pilot’s GPS signal, the testing can end up feeding the pilot incorrect information, leading to thinking they’re somewhere they’re not.

Each tangent the article goes on reveals worrying new details, like how pilots are warned that testing may be happening, often leading to smooth flights and a “Chicken Little” situation where pilots have heard false warnings so many times that they’re not prepared for when it actually happens. There are also hints that the problem may be happening more often than even the Federal Aviation Administration realized.

It’s some necessary reporting. Without the public being aware of the problem, there won’t be any calls to stop or bring greater transparency to the testing. When the military carried out tests of nuclear bombs, it was at least obvious to people that something was happening, even if they were unaware of the radioactive particles (literally) raining down on them. Sometimes, pilots don’t even know that the military carries out GPS-jamming tests. So far, it doesn’t seem like the tests have killed anyone, but reading about the close calls described in the piece is harrowing, and it’s definitely worth your time.