Passage: Chkalov achieved several milestones in aviation. In 1936 and 1937, he participated in several ultra long flights, including a 63-hour flight from Moscow, Soviet Union to Vancouver, Washington, United States via the North Pole in a Tupolev ANT-25 airplane (18–20 June 1937), a non-stop distance of 8,811 kilometres (5,475 mi). The flight pioneered the polar air route from Europe to the American Pacific Coast.

Question: What was Chkalov's specialty?
aviation