National Aviation Day is observed on August 19, 2018. The National Aviation Day is a United States national observation that celebrates the development of aviation. The holiday was established in 1939 by Franklin Delano Roosevelt, who issued a presidential proclamation which designated the anniversary of Orville Wright's birthday to be National Aviation Day.
The proclamation was codified, and it allows the sitting US President to proclaim August 19 as National Aviation Day each year, if desired. His/her proclamation may direct all federal buildings and installations to fly the US flag on that day, and may encourage citizens to observe the day with activities that promote interest in aviation. (With material from: Wikipedia)