Character mistake: After firing Percy and Baldrick, Edmund says to Baldrick that he'll probably go back to shovelling dung in the gutter where Edmund found him. In the pilot episode The Foretelling, Edmund actually met Baldrick when Baldrick was pouring a drink for Edmund.
Continuity mistake: When Blackadder's plane is shot, we see the bullets hit the side. In the next shot of the plane, not only is the side intact, but fuel is coming out of the bottom.
Visible crew/equipment: During the general's speech about how Blackadder is the person to organise a concert party, look at the entrance to the trench. In one shot you can see a crew member moving a giant cloth. You see mostly the movement, but you can catch a glimpse of the crew member's face. (00:06:50)
Other mistake: When we first see the plane that Blackadder and Baldrick are flying, the machine gun on top of it is firing. There are 3 mistakes here. 1) We don't hear the gun fire. Cannot be argued by the plane drowning it out, as we later hear the Red Baron's gun firing. 2) In the next shot, the gun has stopped firing. 3) The fact the gun is firing is ignored by Blackadder and Baldrick. They are too busy on keeping the plane level - the whole flying scene was obviously archive footage of WWI planes flying.
Suggested correction: OK a few points. 1. The baron and Blackadder are flying different kinds of plane. One could be louder than the other. 2. Gunners have to stop occasionally. So the gun stopping isn't a mistake. 3. We don't know for definite if they are ignoring the gun. This is speculation at best.
