Updated version of Black Walkers, Silver Flyers attack fast and hard in Space Channel 5 Part 2. They appear in "Report 4: The End for Space Channel 5?!" as the first enemy Ulala encounters. They're not that tough though and all Ulala has to do is aim right to bring them down quick.
It can be speculated though that the Silver Flyers were actually the "robot babies" stored inside Kin, Kon, and Kan and thus made an earlier appearance in Report 1.
"Surface is coated with solar metal for outer-space activity. This model boasts a bodyslam attack that takes advantage of the upgraded speed and durability."