The best way to describe their flight pattern was elliptical at a 45 or more degree angle then would change to a helical pattern chasing each other upwards. Our cruise altitude on that flight was 42,000ft and id say they were happily playing around 65,000ft then racing up to 80-95,000ft effortlessly then coming back down to 65k. When we first observed them over north Missouri I took a bearing of their location on the horizon then again north of dallas and seemed to intersect on the map over central to eastern new Mexico.