Manfred von Richthofen, better known as the Red Baron, was a famous ace pilot.
He taught the Doctor to make a barrel roll. (PROSE: The Secret in Vault 13)
According to the Third Doctor, the Red Baron liked to approach his adversaries from the direction of the sun. (PROSE: Doctor Who and the Planet of the Spiders)
Jack Harkness was once compared to Red Baron by Allen Shapiro on account of his World War II coat, commenting "What is it with you, Red Baron? You got Snoopy up your ass?" (TV: End of the Road)
As the Doctor's TARDIS was out of control, it materialised in front of the Red Baron's biplane as he was about to shoot down a British recce pilot. Both the Baron's plane and the TARDIS, with the Fourteenth Doctor and Donna Noble inside, were briefly captured by the Brigade of Gübernators in their plan to hijack him as one of history's most skilled pilots, but the Doctor freed them as the TARDIS took off again. The Doctor promised Donna that history would deal with him, leading her to joke that she knew how Snoopy would get him. (COMIC: Untitled)
Behind the scenes
In the real world, Manfred von Richthofen was a German ace pilot active in World War I. Several German military aviation squadrons were named after him. Some of them are mentioned in-universe. For instance, Hermann Goering is stated as "commander of the famous von Richthofen squadron" in the novel Timewyrm: Exodus, but no connection to the Red Baron is made there. His real name would not be connected to his nickname until the release of Untitled in DWM 598.
Shapiro and Donna's comments are in reference to a running gag in the Peanuts comic strip where Snoopy would battle the Baron.