U.S. Air Force 1st Lt. Matthew Alexander secures his MBU-20/P oxygen mask before a training mission on Lask Air Base, Poland, March 18, 2014. Alexander, a pilot, is assigned to the 555th Fighter Squadron. U.S. Air Force 1st Lt. Matthew Alexander secures his MBU-20/P oxygen mask before a training mission on Lask Air Base, Poland, March 18, 2014. Alexander, a pilot, is assigned to the 555th Fighter Squadron. SHARE: Download: Full Size (3.93 MB) Tags: Photo Essays Credit: VIRIN: 278075-C-HFZ34-452.jpg Photo Gallery