I think it was a pair of large military jets similar to a c-17 but I am only guessing by the load sound of the jet engine. Judging by the strobes There were at least two jets flying in a straigt line due south approximatley 1/4 mile apart at near or about 15,000 feet from sea level. They were maybe flying around 380-400mph or so.Hill field is an hours drive from here however, in my 30 plus years of living here I have never seen a commercial or military plane take this route or fly this low unless it was on the fourth of july for a fly over. Also the planes did not head back to the base they continued on a southerly course.I am just curious as to why they were flying where they were and why were there two of them. The activity is just a bit strange from what I had seen in the past.Wonder if anybody knows what they were up to?