I started working as a mechanic on turboprop airframes and engines in an airline industry that had inducted the Boeing 737-200 in its fleet at the time of my joining.
When I qualified as an engineer and started certifying, I was looking for an opportunity to work on the Boeing 737-200. Finally, after a few years, I was qualified to certify the 737.
During my 10 years of certification there was not a single instant of grounding. The airplane was a warhorse and dependable.