Although the Speeds to Fly that we have been discussing so far are the ones that will let you glide to that safe landing spot if any will, they are too slow to win contests and too slow for most cross-country flights. In these cases we are more interested in covering the ground in the shortest time rather than obtaining the flattest glide. That introduces a new definition of Speed to Fly. Credit for developing this concept of Speed to Fly is usually given to Paul MacCready, and the speed ring discussed earlier is usually called a MacCready speed ring. Cross-country flights utilizing thermals consist of alternately climbing in one thermal and gliding to the next. MacCready noted that the Speed to Fly between thermals should be based on the strength of the thermals. If the thermals are strong you can fly faster than the speed that produces the flattest glide. You will lose more altitude, but you make up for it by climbing faster in the next thermal. Thus you reach the top of the next thermal sooner than you would have at the lower speed.