Combination of both. There's a reason aviation is many times safer than driving and an expensive field to play in. It came slowly though. An old engine or air

Combination of both. There's a reason aviation is many times safer than driving and an expensive field to play in. It came slowly though. An old engine or airframe means they're well understood and don't trigger need for re-certifying. Every time an issue is found or production improvement is made it'll show up in EASA or FAA revised certification, maintenance schedules, time between checks, or even how you're allowed to operate it. Every identified accident cause filters into the system similarly. A famous case came when jet liners were new, in the early 50s. The ground breaking DH Comet, and the world's first jetliner, was mysteriously falling out of the sky [1] with loss of all on board after around a year in service. That was when the world learned about metal fatigue in airframes and stress points. If it hadn't been DH it would have happened to Boeing or someone else [2]. The legacy was such that DH lost commercial opportunity for half a decade, and the world started along the track to a recognisably modern accident investigation and aircraft certification regime. Histories of that period in aviation are fascinating as it was also a particularly vibrant period as all the wartime progress was applied to lots of new designs of civil aircraft. I'm not sure the thresholds differentiating between "it's a new engine now, full prototype testing and certification please", and the aviation equivalent of a revision note, but it seems incredibly low. Those Lycoming engines don't even put out a few more bhp than they did when newly designed back in 1950-something. A simple improvement in say carburettor design that would see a car maker just add the change doesn't happen easily in aviation. That's so some vanishingly rare circumstance doesn't cause it to fail in service with associated loss of life. I dread to think what GA or Transport certification runs in at, but plenty have gone bust trying to make better GA planes or engines. Microlight, Light Sport and homebuilt (lightly certified) sectors have dozens of interesting weird designs and ideas, and experiments with new materials. Even with all that mistakes are made, and people die, especially with new designs. The deaths stop much more quickly than in many other fields. When a helicopter like a Super Puma, favourite of offshore operators, a 40 year old relatively simple airframe and engine has a $15m price tag faster progress becomes prohibitive. It's the aviation equivalent of a minibus. Just it's a very safe minibus with bookshelves full of accident history and safety revisions. [1] https://en.wikipedia.org/wiki/De_Havilland_Comet https://en.wikipedia.org/wiki/De_Havilland_Comet [2] https://en.wikipedia.org/wiki/De_Havilland_Comet#Legacy https://en.wikipedia.org/wiki/De_Havilland_Comet#Legacy (relevant section)