3 stars moving in a triangular formation accross a very clear sky

My brother and his girlfriend were outside smoking when my brother saw 3 star-like objects moving, north to south, slowly through the sky in a "greater than symbol" (>) formation.  I was already in bed, but my brother woke me up.  By the time i got outside (maybe a minute) the formation had moved to the far south side of the sky.
 For the minute i was outside, i saw the formation increase its speed and altitude, until each star seemed to reach an altitude that was no longer visible.  One star at a time disappeared, in succession until they were all 3 gone.
 If you weren't paying attention, you would not have noticed them moving.  They looked exactly like stars, they were shimmering and their altitude gave them a slow moving illusion.