Depends on what you consider starting. 16 years is probably the most reasonable number, but you could argue for as little as 6. Initial work on Dragon began in

Depends on what you consider starting. 16 years is probably the most reasonable number, but you could argue for as little as 6. Initial work on Dragon began in 2004, it ‘entered service’ in 2009, had its first mission in 2010, but first connected to the ISS in 2012. https://en.wikipedia.org/wiki/SpaceX_Dragon https://en.wikipedia.org/wiki/SpaceX_Dragon Work on a crewed version was officially mentioned in 2006 though they only got a contract for manned missions in 2014 and the first manned mission was 16 November 2020. https://en.wikipedia.org/wiki/SpaceX_Crew-1 https://en.wikipedia.org/wiki/SpaceX_Crew-1