I also live in Quincy,IL and was startled to hear the same extremely loud jet like roar over my house. It was about 2 weeks ago so I’d guess mid July 2019 and it was approx 1 am when I stepped out onto my back patio to enjoy the summer night air when suddenly, out of nowhere, this loud roar started and the only way I could describe it was that it was like a very loud and very big jet engine was somehow suddenly in my front yard. It was so loud that it seemed like it was everywhere but also literally right over my property. I listened to it for about 45 seconds then decided to run in and grab my phone and mt husband so I wouldn’t seem crazy trying to explain this. By the time I got back outside, probably 15 seconds later, before I could even get my camera up on my phone, it suddenly stopped. Just as quickly and suddenly as it started. My husband hadn’t even made it out there yet. It has blown mt mind ever since and I’ve been watching videos on you tube and researching other people’s experiences. I just wish I knew what the Hell it was cuz it was bizarre. Everything I seem to find on it leads to believing it’s cloaked UFOs. I never believed they existed but now I’m really starting to wonder if they do.