Day of the Diesels is a 2011 CGI feature-length special and film of the TV series, Thomas & Friends. The film's CGI animation is by Nitrogen Studios.
After witnessing a new engine, Belle, extinguish a fire, Thomas and Percy shunt her to the Steamworks when she runs out of water. Once there, Sir Topham Hatt congratulates her, but says they need another fire engine. When Belle suggests Flynn, the matter is arranged to bring him over from the Mainland.