Propelled by war, technology advances quickly.
When my father enlisted in the US Army Air Corp in 1936, he was trained as an aircraft mechanic, working on the B3 bomber, a canvas covered biplane bomber with a tiny payload:

The B3 bomber was state-of-the-art in the 1930's
War is hell, but it also drives amazing technology, and in less than 20 years, America went from creaky biplanes to the B-52 Bomber, introduced in 1952:

In less then 20 years, America went from the stone age to the jet age
After the nightmare of December 24th 1945 when the USAF destroyed their entire inventory of B-17, the government said “never again” and they began hanging-on their old warbirds.
Interestingly, the USAF plans to keep the B52 in service for 100 years, and does not plan to retire then until the 2050’s.