UFO Buzzes Train from London (Video)

A UFO, or possibly a pair of them, buzzed past a train traveling from London to Leeds and was caught by a passenger filming the snowy scene outside the window. What is it?

The incident was caught on video and uploaded to YouTube without much description and no commentary on the clip itself. As the train makes its way between the two cities, suddenly two flashing orbs streak by above until they seem to disappear into the cloudy, snow-laden sky.

The orbs are circular, silvery, and flying at an incredible speed. They don't appear to be a lens anomaly or a reflection of lights inside the passenger cabin. The UFO flits by quickly, but the segment is slowed down in the second half of the video. It doesn't help to pinpoint exactly what the unidentified flying objects could actually be.

The object don't resemble any known type of aircraft, lacking wings and not trailing exhaust.

So, what is it?

Here's the video: