Hogan says that it is OK if the Luftwaffe inspects the P-51 since it has a German engine. The engine was not what made the P-51 such a great fighter, it was the design of the plane itself so the Germans would gain a lot of information from studying it.
A US Army air crewman tells Hogan he has just flown his 50th mission, and his tour of duty is therefore ended. US Army air crewmen were allowed to return home after flying fewer missions than that--25 to 35, depending on how late in the war their tour of duty occurred.
Hogan agrees to steal one of the new Mustang fighters for the Germans. However, the model he steals is the later bubble canopy P51D. If the Mustang had just appeared, Hogan should be stealing the P51B razorback version.
Hogan and Klink steal a P-51; a closeup of Hogan operating a yoke as they takeoff. P-51s had sticks, not yokes. The scene was either filmed in a bomber cockpit or else the wrong stock footage was used.