Reliability

In fact, improvements in metallurgy have driven improvements throughout the history of aviation. The biggest bugaboo for airplanes, which will come as no surprise to those of us who are pilots, is the engines that power our planes. Recently, I watched a video of a DC-6 taking off from the fog in Anchorage. What I thought, honestly, was, that sound is amazing! And, what a beautiful plane! But mostly I was thinking, how the heck do they manage to keep all four of those double-row radials running at the same time? The engines, as you might know, are marvels at squeezing the very last ounce of practicality out of a technology, in this case, the radial engine, or, if you will, the internal combustion reciprocating engine. The only way those marvels happened and could have happened is that by the 1930s, metallurgy had improved to the point that such engines could work because the metals were stronger and more heat tolerant, and the tolerances of their manufacture were so much finer than even a decade before. 

These improvements in materials and manufacturing led to turbine engines becoming reliable and practical options, and turbine engines changed everything.