"Lines" of latitude on Earth are actually circles. The Tropic of Cancer is the northernmost line of latitude at which the Sun appears directly overhead at noon. The Tropic of Cancer has a radius of 5854 kilometers. To qualify for an around-the-world speed record, a pilot must cover a distance no less than the circumference of the Tropic of Cancer, cross all meridians, and land on the same airfield where he started. a. The minimum distance that a pilot must fly to qualify for an around-the-world speed record is about kilometers. Question 2 b. Estimate the time it would take for a pilot flying at an average speed of 1231 kilometers per hour to fly around the world. At this speed, it would take about hours.