Object was 1,000 feet behind a medium sized plane, caught up and then was flew beneath it. Flew away South-East at incredible speed.

Sunny and cloudy, fair weather background. As mentioned, there was an object gaining speed on a low flying medium sized plane which was probably a mile away from us. Once we got a good look at the plane, we noticed the oval object catching up to it. The UFO seemed to have a very resolute and direct flight path compared to the plane, meaning it was not another plane, it was not a glider and it was not a large bird. After the object caught up and flew a few hundred feet under the plane, it changed directions and shot off southeast and completely disappeared. My friend and I talked through what it could have been, but we quickly agreed it had to be a UFO. We wish we took a video or were closer, but we were just mesmerized by what we were witnessing.