3 stars moving in a triangle formation near the Minnesota-Canada border?

I was camping with a friend in the northern Minnesota woods. It was very dark at night, and we were very clearly able to see the stars in the sky. While watching, we saw what appeared to be 3 stars moving in a straight line across the sky. Whatever the stars were, they appeared to be very, very high in the sky. Looking up, they appeared to be less than an inch from each other, but as high as they were, they could have been a couple of miles apart. I've seen one star move before, assuming it to be a satellite or jet plane. This is the first time I've ever seen 3 move together in what appeared to be formation. There was a single star out front and 2 other stars behind it side by side, in a triangle formation. The stars continues across the sky and we watched until we lost sight. They were travelling from southwest to northeast (into Canada)
We wonder whether the witness means a duration of 30 seconds, not 30 minutes.  We will correspond with him to clarify that point.  If it is 30 seconds, he may have been witness to the "triplet" of satellites that are reported to our Center quite frequently, and which are thought to be U. S. Navy satellites, which orbit in formation.  PD