Other mistake: During the missile attack on the bomber, the radar operator is calling out closing distances to the approaching weapon and they are consistent with the 10 mile calibration rings on his scope. As the missile gets around the 20 mile range, the distances he reports are no longer consistent with the scope.
Other mistake: When the radio operator opens the Aircraft Communications Codes book, he turns first to a 'L' page, but all the codes are 'F' codes including the key code. He then turns to a 'J' page and again the codes are the same 'F' codes. He then turns three 'E' pages, pages one and three are identical.
Factual error: During the B-52's final destination bombing run the bombardier counts down the distance from target to the crew. The beginning distance starts at 10 miles from target down to 3 miles at the rate of 1 mile per minute or 60 mph. A B-52's minimum cruising speed is about 300 mph, which calculates to traveling a mile every 12 seconds. (01:17:10 - 01:22:50)
Answer: Peter Sellers improvised it. During that scene if you watch the actor playing the Russian character you can see him trying not to laugh at Seller's performance.