St. Elmo's Fire Air Force KC-10 pilots experience a weather phenomenon called St. Elmo Fire while flying through a thundercloud in an undisclosed location, March 22, 2017. The phenomenon occurs when the electric field around the aircraft causes ionization of the air molecules, producing a glow and sparks easily visible in low-light conditions. Air Force photo by Senior Airman Brian Kelly SHARE: Download: Full Size (3.27 MB) Credit: Senior Airman Brian Kelly VIRIN: 170322-F-ZZ999-002A.JPG Photo Gallery