The Air Force's WC-135 Constant Phoenix aircraft collects air samples from areas around the world where nuclear explosions have occurred. U.S. Air Force photo The Air Force's WC-135 Constant Phoenix aircraft collects air samples from areas around the world where nuclear explosions have occurred. U.S. Air Force photo SHARE IMAGE: Download Image: Full Size (1.18 MB) Photo By: VIRIN: 483163-U-EKL12-502.jpg Photo Gallery