Recorded on Nov. 11, 2011 (or if you prefer on 11/11/11) this video shows an unknown object trailing a C-17 Globemaster III over the U.S. West Coast. Although it is obviously a UFO because it is both unidentified and flying, I don’t believe the object has an alien origin. The distance from the aircraft tail, the position and apparent angle with the flight path make me think to something dragged by the American transport plane, like an undeployed drogue chute used for cargo drop (even if the cargo door seems to be closed) or a pallet that has lost (?) the extraction chute.
Another intriguing theory: the UFO is actually an unknown sensor or antenna.
The green tailband makes the C-17 a 62nd AW plane from McChord AFB, Washington.
Below, a U.S. Air Force image that shows how a C-17 air drop looks like from distance.