This task involves creating questions from a given passage that involve some kind of complex reasoning (including numerical reasoning).
The generated questions must require looking at more than one part of the passage to answer. Try to use a variety of reasoning types in your questions (some of the sample reasoning types are illustrated in the 'positive examples' field) and also have a variety of answer types (spans, numbers, dates). A span is a continuous phrase taken directly from the passage or question. In such questions, the answer spans are recommended to be five words. Questions with answer type "number", are expected to start with "How many". For instance, "How long did an event last?" can be phrased as "How many years did an event last?". To increase diversity, try to create more questions for which the answer will be multiple spans. Please create questions that require AT LEAST 2 arithmetic operations as illustrated in the 'positive examples' field. You are encouraged to try DIFFERENT COMBINATIONS of operations and not just limit to the combinations shown in those examples. The more challenging questions you create, the better it is.
Q: Passage: On 20 September 1939, before the YP-38s had been built and flight tested, the USAAF ordered 66 initial production P-38 Lightnings, 30 of which were delivered to the USAAF in mid-1941, but not all these aircraft were armed. The unarmed aircraft were subsequently fitted with four .50 in (12.7 mm) machine guns (instead of the two .50 in/12.7 mm and two .30 in/7.62 mm of their predecessors) and a 37 mm (1.46 in) cannon. They also had armored glass, cockpit armor and Fluorescence cockpit controls. One was completed with a pressurized cabin on an experimental basis and designated XP-38A. Due to reports the USAAF was receiving from Europe, the remaining 36 in the batch were upgraded with small improvements such as self-sealing fuel tanks and enhanced armor protection to make them combat-capable. The USAAF specified that these 36 aircraft were to be designated P-38D. As a result, there never were any P-38Bs or P-38Cs. The P-38Ds main role was to work out bugs and give the USAAF experience with handling the type.
A:
How many P-38 Lightnings that were ordered from the initial production were not delivered in mid-1941?