Herbert Welsh started his career in aviation in 1951 at Curtiss-Wright working as a test engineer in the experimental propulsion test group. At Wright he worked primarily on the J65 turbojet, and then on the J67 turbojet. In 1958 he moved out West to work at The Boeing Company.

His first assignment was designing ground support equipment for the Bomarc missile. He transferred to the X-20 Dyna-Soar program when the Bomarc missile program was cancelled. Then to the Boeing Turbine Division and then to the SST program. He didn't spend much time in the SST group since the program was soon cancelled; however he transferred to the Renton Change Control group just in time to escape the dramatic Boeing layoffs of the late 1960s.

The Renton Change Control group is the group he spent the majority of his 34-year career at Boeing. During his career in the Renton Change Control he worked on many Boeing Commercial models (707AWAC, E-6, 727-100, 727-200, 737-200, 737-300, 737-400, 737-500, and 757-200). He retired as the manager of Renton Change Control Group in 1992.

His legacy continues at Boeing with his two sons (Bryan and Dylan) who are currently working as flight test engineers in Seattle.