For influence I think the Comet must be on the list. The first jet liner, 1952, which, although a step forward in flying also had it's disasters with metal fatigue. However, as wiki says - the aircraft's legacy does include numerous advances in aircraft design and in accident investigations. The inquiries into the accidents that plagued the Comet 1 were perhaps some of the most extensive and revolutionary that have ever taken place, establishing precedents in accident investigation; many of the deep-sea salvage and aircraft reconstruction techniques employed have remained in use within the aviation industry.

It's been said that, without the Comet, Boeing wouldn't have pushed for the 707 so fast.