unexplained craft

The craft my stepmother and I saw was huge and it had 4 lights on the bottom of it, about 50 ft tall and 50 -70 feet across. We had just left dairy queen and on our way home we were passing what was an empty field at the time,and about 60 yards away and 20 feet up in the air we saw this shiny object shaped like a giant toaster. I told my stepmother to flash her headlights at it and after she did it began moving away slowly with a low hum that you could barely here. All of these years I never stopped thinking about it and figured it could have been a military project from SAC (strategic air command) airforce base in Bellevue, NE, because that was the way it traveled after we flashed our lights at it. But I also wondered why it would have gone to such a residential area when there were so many more empty fields closer to the base.
Date is approximate.  PD