Given the task definition and input, reply with output. In this task, you're given passages that contain mentions of names of people, places, or things. Some of these mentions refer to the same person, place, or thing. Your job is to write questions that evaluate one's understanding of such references. Good questions are expected to link pronouns (she, her, him, his, their, etc.) or other mentions to people, places, or things to which they may refer. Do not ask questions that can be answered correctly without understanding the paragraph or having multiple answers. Avoid questions that do not link phrases referring to the same entity. For each of your questions, the answer should be one or more phrases in the paragraph, and it should be unambiguous.

Passage: World War I veteran Waldo Pepper feels he has missed out on the glory of aerial combat after being made a flight instructor. After the war, Waldo had taken up barnstorming to make a living. He soon tangles with rival barnstormer (and fellow war veteran) Axel Olsson.
Antagonistic at first, Waldo and Axel become partners and try out various stunts. One of these stunts, a car-to-aircraft transfer, goes wrong and Waldo is nearly killed after Axel is unable to climb high enough to clear a barn, slamming Waldo into it.  Waldo then goes home to Kansas to be with on-again, off-again girlfriend Maude and her family. Maude, however, is not happy to see Waldo at first; because every time he returns from a barnstorming tour of the country, he is injured in some way. Eventually, however, they make up and become lovers once again. Meanwhile, Maude's brother Ezra, a long-time friend of Waldo's since boyhood, promises to build Waldo a high-performance monoplane as soon as he is well enough to fly it. Waldo's goal is to become the first pilot in history to successfully perform an outside loop, and Ezra feels Waldo can do it with the monoplane.
What is the full name of the person who tangles with a rival barnstormer?