Filming a T-38 in flight and saw a UFO in the video

I was filming a T-38 on its approach to land at Mather Airfield and I noticed an object that flew into frame rather fast. I’ve lived near this airfield for 30 years, even when it was an Airforce base and have never seen any aircraft come close to another aircraft. When I slowed the video down to watch frame by frame, I noticed that it did not look like any other aircraft I’ve ever seen. It was spherical in shape and had some sort of vapor coming out of the back of the craft. As it moved forward the vapor seemed to move from the rear to the sides. It was also flying faster than most aircraft I’ve seen in the area. It was dark metallic looking (from what I could tell) however at on point light seemed to reflect off of it. It vanished just as quickly as it showed up.