Three bright lime green luminous oval objects traveling at high rate of speed across night sky

As this happened years ago, but have never seen this type of event again, I do not know what to make of it.  It was a summer evening right after a dinner party with a friend who has since passed away.  It was a very clear summer evening and as we were going to our vehicles to leave, 3 bright lime green luminous oval shapes went from north to south at a speed I would say is equitable to a jet.  The color was captivating and they were solid in color.  There was one in front and two at the rear, quite close to each other.  They were also, I would say, about the length of a Boeing 707, very large and actually quite low in the sky.  I couldn't even begin to tell you what height I thought they were, just that they looked low on the horizon and not quite straight overhead.  They went in a straight line of flight.  I have often thought about this and have never read anything that could explain what we saw.  There was no sound, which was strange for something traveling that low and that fast.
Date is approximate.  PD