I'm not sure if this is the biggest UFO orb in history or the explosion of a malfunctioning Russia Soyuz rockets after a space ship carrying tonnes of cargo for the International Space Station (ISS) crashed into Siberia shortly after blast-off that happened on the same day. I will post it and let you decide. Perhaps the crash took place not in Siberia but...Shanghai or perhaps the Russian Soyuz entered China airspace and was shot down. SCW
Update on March 2015: Old video was down so I found another and posted it below.
Date of sighting: August 25, 2011
Location of sighting: Shanghai, China
Dozens of people spotted an unidentified, glowing object above Shanghai and Beijing at the same time. The giant ball of light appeared Saturday night. A pilot flying from Shanghai to Changchun was the first to post information about the colossal light online. The pilot says the so-called "UFO" grew in size and ended up being about 100 times larger than the moon. He said the sphere slowly faded as it hovered above Shanghai for nearly 20 minutes. An expert from Shanghai UFO Research Center suspects the UFO could be the fragment of a satellite launched by Russia two days earlier.