Why don't airplanes fly in straight lines?

Why aircraft don't always fly in straight lines ... So you would think that they would fly in perfectly straight lines from the departure airport to the destination airport in order to minimise fuel burn. ... Map showing the curved trajectory of an airplane travelling between Vancouver and Paris over Greenland. read more

John Cox, special for USA TODAY Published 5:03 a.m. ET June 24, 2013 | Updated 8:11 a.m. ET June 24, 2013 It is shorter to fly the Great Circle route than a straight line due to the circumference of the earth being so much greater at the equator than near the poles. read more

This straight line is modified slightly as airlines must plan flights over fixed points or on fixed airways which don't line up perfectly with a great circle. So that's why you will feel the occasional turn while enroute. read more