An aerospace engineer was an engineer that specialized in the field of aerospace engineering; that is, the branch of engineering that focuses on aircraft and/or spacecraft.
Shannon O'Donnel was an aerospace engineer who worked for NASA during the late 1990s. According to Gerald Moss, she lost her job due to "all this downsizing in aerospace," stating that "engineers aren't given the respect they deserve." (VOY: "11:59")
An archaic term for aerospace engineer was a rocket scientist, a career that was often perceived as being extremely difficult to master. When Loomis became paranoid about being caught by the police for kidnapping several individuals from the blood bank he worked at after Damron requested him to kidnap two more individuals, Loomis said "look, as soon as they figure out that all these people here have been to the clinic, it won't take a rocket scientist to point the finger at me." (ENT: "Carpenter Street")