The word ascension describes the act of rising up through the air. When a plane takes off, it is in ascension, or rising up in the sky.
The noun ascension derives from the Latin word ascendere, meaning "to mound, ascend, go up." You may have observed the ascension, or rising, of a star above the horizon with your telescope. Watching the ascension of a space shuttle up into the earth's atmosphere can be a thrilling experience. The ascension of a hot air balloon up into the sky can be a beautiful sight on a summer's evening.