UFO stands for "Unidentified Flying Object" which is generally taken as a term from which one begins research. A UFO could be anything. A plane, a bird, a meteor, alien space craft, alien drone, anything. UAP stand for "Unidentified Aerial Phenomenon"... this means an investigation has already taken place and stuff like planes, birds and meteors, or balls of lightning etc. have ALL BEEN DISQUALIFIED AS PLAUSIBLE EXPLANATIONS.
As per a freedom of information request by To The Stars Academy Of Arts & Sciences, the US Department of Defense at the Pentagon has released THREE videos (which are also available to regular media through a Freedom of Information Act) with objects they believe to be UAPs and not UFOs, i.e. natural phenomenon and known technologies have been discarded as an explanation by the military.
Here is the first UAP (UFO) video from 2004 (These first two videos can also be viewed at the NY Times article, Glowing Auras and 'Black Money': The Pentagon's Mysterious U.F.O. Program)
Official DoD Video from Stars Academy: Gimbal (2004): The First Official UAP Footage from the USG for Public Release
The second one doesn't have much information.
Here is the second video from 2004;
Official DoD Video from Stars Academy: FLIR1 (2004): Official UAP Footage from the USG for Public Release
Stars Academy Analysis: At 1:14, the object suddenly and instantaneously accelerates to the left, out of view of the sensor at what appears to be unprecedented velocity without a sonic boom or other associated tell-tale signatures of a conventional craft. The acceleration is so high that the sensor cannot maintain track. This type of flight performance cannot be achieved by any known aircraft. Read full analysis here.
The third video is from 2015 and shows the amazement of the pilots which does indicate we are watching something amazing as far as speed is concerned (This video is also in USA Today: UFO encounter? New footage shows U.S. Navy pilots' apparent sighting of alien craft near East Coast );
Official DoD Video from Stars Academy: Go Fast (2015): Official USG Footage of UAP for Public Release
Read analysis here.