What is the first in-flight refueling?

The first in-flight refueling occurred on June 27, 1923, when a U.S. Army Air Service De Haviland DH-4B aircraft transferred fuel to another DH-4B. This historic event was conducted by Lieutenant John A. Macready and Lieutenant Oakley Kelly, demonstrating the feasibility of extending flight ranges through aerial refueling. This pioneering achievement laid the groundwork for modern air refueling techniques used by military and commercial aircraft today.