What does the first "A" in NASA stand for?

The first “A” in NASA stands for Aeronautics. NASA’s full name is the National Aeronautics and Space Administration.

Aeronautics is the science and practice of designing, building, testing, and operating aircraft within Earth’s atmosphere. Although NASA is best known for space exploration, aeronautics has been part of its mission since the agency was created in 1958. NASA inherited major aviation research responsibilities from the National Advisory Committee for Aeronautics, or NACA.

That history is why NASA studies more than rockets and planets. Its aeronautics programs investigate subjects such as aircraft efficiency, turbulence, supersonic flight, helicopter noise, and safer air-traffic systems. The first “A” is sometimes mistakenly remembered as “astronautics,” but astronautics concerns spaceflight; NASA’s name places aeronautics first to acknowledge its atmospheric-flight research as well as its space mission.