On which date did the RNAS join the RFC to form the RAF?

The date on which the Royal Naval Air Service (RNAS) joined the Royal Flying Corps (RFC) to form the Royal Air Force (RAF) is indeed the 1st of April 1918. This merger was a significant moment in military aviation history, largely driven by the need for greater coordination and efficiency in aerial operations during World War I. The establishment of the RAF marked the first time that an independent air force was created, separate from the army or navy, which signified the increasing importance of air power in military strategy. This date is often noted as the birth of the RAF, making it a pivotal point in the development of air forces around the world.

The other dates do not correspond with the merger that formed the RAF; 1st April 1916 is before the formation of the RFC, 1st April 1917 was a year before the merger, and 1st April 1919 is after the establishment of the RAF, which is why they are not correct answers.