I live on a bluff over the Kansas river facing south. I was making a video using my DJI Phantom 3 quadcopter. I flew south over the river and over a lake formed by a sand and gravel pit then turned north and flew back over my house. I cut out some of the video, added some music and showed the video to friends. No-one noticed anything unusual. Later as I was examining the video to see how I could make another one that would be better I noticed a fast moving object heading almost straight at me from 12 o'clock ending a short distance to my left at 9 o'clock. This object appeared white in color and flew a straight line while in the video. The object appeared extremely fast moving. This observation deeply concerned me and I showed it to my wife and a close friend that I have a great respect for to get their opinion. Both stated that it looked very unusual to them. My friend asked "What the he** was that?" The object appears in the video over the far side of the lake. The lake is right at 700 yards across at that point. I was shooting at 30 frames per second and the object is in view for 6 frames. Adding a 7th frames to ensure it was past the near shoreline I calculate that it took 0.233 seconds to travel the 2100 feet. If my math is correct that means it was traveling at approximately 9,068 mph or 11.92 mach.I am including a clip of the video that shows the encounter and I cut the frame out where the object was closest to me. There is a screen shot of that plus I used filters in Photoshop that helps remove blur from an object (high pass and unsharp mask). Those are also included.There were white seagulls flying around the lake at the time, but in the video, as well as physical observations since, I see no behavior that resembles this observation.