Conversation so far:
What is worth seeing in Washington D.C.?
Most prominent at its center point is the Washington Monument, and war memorials include those to veterans of World War II, the Korean War, and Vietnam. ... If you look at a Washington, D.C. attractions map, you'll notice that many of them line the National Mall, so you're likely to spend a lot of time here.
Which Smithsonian museums in Washington D.C. are the most popular?
The National Air and Space Museum was the most visited Smithsonian museum in 2018, with approximately 6.2 million visits.

Question: Why is the National Air and Space Museum important
Self-contained rewrite: Why is the National Air and Space Museum important?