I saw 3 separate red lights flying together-went in a semicircle then went up at the same speed and disappeared.

I was out feeding my horse and it was dark outside. I looked up and to the right and saw 3 red lights flying overhead. The size was about 2-3 times the size of the stars. They flew to the left in a semi circle but not in any sort of formation. They drifted randomly amongst themselves/not too far from one another. As they circled left, I heard the hum of what seemed to be an engine or motor. I kept watching them and as the circle was about halfway complete they went up at the same speed. I kept watching, I was thinking to myself "if these things dissappear, I'm going to ((be very surprised)).." and that's exactly what they did. My sister then came outside wondering why I was taking so long. To be honest, I never asked how long I was out there to know if it was longer than I recall.
Date is approximate.  PD