Sounded similar to a plane, but was triangular and set out on a repeated and definite flight plan!While watching late news, I heard what I thought was an airplane. Didn't think much of it... at first. Every 20-25 minutes I would again hear this sound, traveling from SSE to NNW. After the third time, I went outside onto my deck to try to catch a glimpse of the aircraft I heard at regular intervals. The sky is clear, near full moon, not a cloud in the sky. Beautiful night for star gazing. From the SSE, I first noticed two very bright white lights... much brighter than even medivac's lights would be. As this craft got closer, I heard that familiar sound of what I thought was an airplane. As the craft flew over me, I realized this was triangular in shape with three white lights and one bright red, flashing light in the center, under-side. I followed this craft visually as it continued N then NW...followed along the horizon until it was out of sight due to a ridge of trees and houses. Approximately 20 minutes passed when I again caught this craft in the SW sky. From that point, it was almost exactly 5 minutes before it was once again approaching me from the SSE, continuing along the same path as before. As I am writing of this siting of something, it has again just completed another lap in/around the area. I've searched all sources of media for any way to explain this bazaar siting... nothing... No other witnesses to what I've seen except for my dog!