Thermals are vertically rising air currents commonly created beneath clouds. As Gladics worked his way east, he would slowly spiral his way upward beneath a cloud, gaining altitude on thermal currents. When he calculated that he was high enough, he would head further east, looking for another cloud under which he could ride on thermal currents. While between clouds he would lose altitude. Gladics said his glider's 15-meter wing span enables him to travel 42 horizontal miles for every vertical mile descended in calm conditions.
Winds alter the calculations, however.
You're thinking and calculating the whole time. When he got to Gardiner, he took a photo and turned around, taking aim at Hailey. He repeated the same procedures he used to get to Gardiner. There were points when I thought I might not make it. As he approached Dell, Mont., which is along Interstate 15 in the southwestern part of the state, he had to dump 30 gallons of water he was carrying to help his aircraft travel at greater speeds.