This is a different Quiz Question. It’s possible the answer will never be known. What you need to do is to do some research. Once you have decided on your best answer, post it as a comment and state your defense of your answer. Here it is:
On 17 December 1903 nobody had ever made a flight in a powered, heavier-than-air craft. There were no airplanes in the air. Then Orville Wright flew for 12 seconds, and then he landed, and again there were no airplanes in the air.
On an unknown day a few years later there were no airplanes in the air. Then somebody took off in an airplane, flew it, and landed. But before the airplane landed, somebody else took off in another airplane. Since that time there has always been an airplane in the air.
The Quiz Question is when was the last time there was not an airplane in the air? I am counting only powered aircraft piloted by a person. Post your answer as a comment below. I will select the winner. The best answer wins Donald Trump’s $50 million prize, to be awarded his second day in office as President.