Driving down busy street at night, quarter of mile or so, thought we saw several helicopters in sky. Drove right up to it and under it. Got out of van and discussed what we were seeing. Huge diamond shape with brightest strobing white lights I had ever seen, very low to ground, hovering over neighborhood, no sound. Clearly saw underneath writing or something all under. Airplane came and ufo streaked off . Estimated to be 150ftx150ft. , this may be vast underestimation. No reports. No radar. It was huge. We had plenty of time to examine it.I am a believer and have had one other encounter of disconnected balls of lights examining the car I was in with 3 other people. My mother on the other hand is a devout disbeliever. My sanity is intact because she was with me. The object appeared to be charcoal gray, square or diamond shaped with blinding white strobe lights at the points. No other colors were observed. There was a distinct writing or something underneath in circles that covered the bottom. When we first saw it it was traveling east to west seemingly down a busy street. It got off the street and turned north and just stopped as if to let us look at it. It just hovered over a populated neighborhood not doing anything. It seemed to be about 50 ft. above the houses, very low. It was huge. We discussed wondering how such a thing could fly. From the direction of the airport (east) we saw a very fast flying airplane coming our way. The thing took off at a high rate of speed north and we gave chase along with the airplane. We kept it in sight for another 6 miles and then lost it. I called the airport to ask if anything had been reported and they said no. I have searched everywhere and cannot find a picture of this thing and wonder if anyone else has seen this particular one. It took so long to report because I didn't know where and got my computer for Christmas.