Which of the following categories does not include aircraft under 90' wingspan?

The correct choice is based on the understanding of the categories of aircraft sizes defined by wingspan. The category specified as "90' - less than 126'" inherently includes aircraft that have a wingspan starting at 90 feet, which directly contradicts the question, as it specifically asks for a category that does not include aircraft with a wingspan under 90 feet.

To clarify, the other categories, such as "Less than 90'", clearly only cover aircraft that are less than that specified wingspan. The categories "200' or more" and "159' - less than 200'" are also above the 90-foot mark and do not contain smaller aircraft. Therefore, the category focusing on a range that starts at 90 feet fails to meet the requirement of excluding aircraft with a wingspan under 90 feet, making it the only choice fitting the criteria laid out in the question.