Why is St. Thérèse of Lisieux a patron of aviators?
The short answer
During World War I, soldiers on both sides reported visions of a young nun comforting the wounded and began carrying her picture into battle. She became a special favorite of French pilots, which began her patronage of aviators.
In the early twentieth century Thérèse's spiritual testament, Story of a Soul, became a sensation in Europe and then worldwide, winning her many devotees. Students of her life call this period the "storm of glory," for the many favors reportedly obtained through her intercession.
When World War I broke out, soldiers on both sides reported visions of a young nun (Thérèse was not yet canonized) comforting wounded men of various nations along the lines. Many soldiers began carrying her picture into battle. She became a special favorite of French pilots, and that is how her patronage of aviators began.