The words "LO Flight Test" describe a "Low Observable" flight test, in all probability a radar measurement test for a stealth aircraft using the radar measurement range at Groom Lake, Nevada. The date of this particular flight test is unknown, but the test reportedly involved a B-2 stealth bomber. The sigma symbol in the middle of the patch refers to the unknown value of the aircraft's radar cross section (sigma/zero being the ideal radar cross section measurement for a stealth plane). "Huge deposit" indicates the bomb load deposited by the bomber on its target, while "no return" refers to the absence of a radar-return, meaning that the aircraft was undetectable to radar. It is unclear why there is a star on the tail of the sigma, though it may simply be an artistic touch. Reference image and text from "I Could Tell You But Then You Would Have to Be Destroyed by Me", by Trevor Paglen