Formation of 4 round/oval craft over Los Angeles at night (no strobe lights)I landed at Hawthorne airport in Los Angeles at approximately 9pm in a small piston airplane. I parked the airplane and was waiting for my guests to arrive when I noticed what appeared to be 4 aircraft approaching from the west. They caught my attention as they were dimly lit with steady lights (i.e. did not have any flashing lights) which is not typical of aircraft (airplanes/helicopters typically have flashing lights). It was somewhat hard to determine what the craft were as they were coming towards my location so at times it appeared as though they were craft coming towards me, and because of this viewing angle, it also appeared as thought someone may have simply let go of some circular balloons that were floating "up" and may just be reflecting city lights from below (as objects at a constant altitude that are approaching you in the sky also appear to be moving "up"). Once the objects moved much closer I was able to determine that the! y were not balloons floating up but were indeed a formation of 4 separate objects flying from west to east directly overhead. The craft flew directly overhead at what appeared to be considerable altitude (it's extremely difficult to judge, but I would estimate anywhere from 5,000 to 20,000 feet in altitude. It was very difficult to determine the shape of the craft, as it was night time, but the craft appeared to have lights on the bottom that either outlined a somewhat circular shape or would "move" in such a way as to be consistent with a circular TV screen with various pixels turning on and off. They were clearly all separate craft as they flew in loose formation and changed position in relation to one another, but generally maintained a somewhat traditional formation consistent with a group of aircraft (i.e. all moving in the same directly with somewhat equal spacing, with the space between the craft roughly 5-10 times the length of each craft). They appeared to move generally in a straight line at a speed consistent with a highe r flying jet or a lower flying helicopter, yet the shape of the objects was neither of these things, and the light patterns of each were slightly different. The light patterns almost appeared reminiscent of the large TV type display contained on the side of the Goodyear blimp, yet much more dimly lit. One craft appear to be completely constantly lit in a circular shape. The center was dark with increasing light towards the edges and slight color variation moving form center to edge. The other craft shared this same general characteristic and color pattern, but the "lights" themselves were not steady state (i.e. the entire circle was not always "lit up" at one time). One craft was lit in such a way as it looked light a two bladed helicopter rotor slowly spinning and fading a trail of fading light behind it (i.e. one line drawn across a circle that rotated and cast a fading trail behind). This appeared to rotate at a speed of roughly once every 3-5 seconds ! (i.e. MUCH slower than a helicopter rotor system). This object was the third in line. The 4th object had a light patter which appeared to be a somewhat loosely drawn triangle which seemed to constantly "morph" and change position and shape within the context of the larger circle (like a screen saver on a computer screen). The objects did not appear to make any noise, however this is not unusual of aircraft in the area as the wind, distance, and city noise can easily drown out aircraft noise.I am a helicopter and jet pilot with 14+ years of flying experience and do not believe these craft to be civilian helicopters or airplanes.I had a substantial amount of time to observe these craft (several minutes?) and attempted to take photo with my iPhone, however given the distance and the night time, I was not able to get a quality photo (again, to be expected given the conditions and equipment used).After the craft had passed overhead, and while they were still in plain view towards the east of my location, I called the Southern California Terminal Radar Approach Control (TRACON), 858-537-5900, and asked if they were tracking any formation of aircraft in the area. The controller initially said they often routed "downwind" traffic for LAX over my location. I indicated that the objects I was referring to were not downwind airliners headed to LAX, but rather were a group of 4 strange objects which now appeared to be well east (perhaps over fullerton airport) and were continuing to travel east bound. TRACON employees indicated that they were not tracking any objects in that area, and said they were "Looking at the radar right now," and did not see anything that fit this description or any other unusual traffic or radar targets.The objects continued to move east and eventually faded from view (as any aircraft would).