The first half hour of the flight was a little unsettling to Ty’s stomach as Kath Two made a few sudden maneuvers, perhaps because she had sensed good air in one direction or bad in another. People who were accustomed to flight in powered aircraft frequently had trouble adjusting to the unpredictability of gliders, but Ty, who had done it before, understood that Kath Two was just hunting for the right way to inject them into the mountain wave hovering invisibly in the upper atmosphere above the Andes crest. He knew she had found it when the juking and jiving stopped and the back of the seat pressed him forward with palpable acceleration. They were in level, steady flight now, proceeding north at something like three hundred kilometers per hour. Kath Two’s task henceforth would be to look far into their future with her lidar-enhanced sensorium and make small adjustments needed to dodge pockets of rough air.