There are so many factors, and these are such low-frequency events, that while I admit to being worried
about such things I shrug it off in terms of decision-making. Who remembers what kind of aircraft was involved in the infamous ValuJet crash? That was a crash caused by careless maintenance, and it wasn't even maintenance of anything obvious like the engines, but of the emergency oxygen generators. So, refreshing my memory by reading the Wikipedia article, ValuJet Flight 592
...airline already had a poor safety record before the crash... known for its sometimes aggressive cost-cutting measures. Many of the airline's planes were purchased used from other airlines, little training was provided to workers, and contractors were used for maintenance and other services. The company quickly developed a reputation for its lax safety...
It seems that it was a Douglas DC-9. In terms of design safety, is that considered a relatively safe or problematical design? Who knows? Not I. The DC-10, there was a cargo door problem related to design issues. But I can't remember anything good or bad DC-9's. It seems to me that the DC-9 must be safe when operated safely, and dangerous when operated by ValuJet.
All these darned aircraft are not really one design, they are built for decades, it's never just a "Cubeb Skyplaster 703," it's always like, 703 model 100, 703a model 200X, 703-300 Grande, 703-310G Transoceanic, 703-5000 Big Gulp, etc. And the 737 Max debacle underlines the fact that airlines order them with different kinds of optional equivalent.
And the same model of airliner may come with a choice of different kinds of engine, and there can be problems specific to one kind of engine.
So even when you read about some problem you don't know if it applies to the particular
model you're flying.
Older aircraft designs, well, the physical planes are probably safe if maintained properly. Again using Wikipedia, "The B-52 completed sixty years of continuous service with its original operator in 2015. After being upgraded between 2013 and 2015, it is expected to serve into the 2050s." And the longer they've been in service, the more likely it is that flaws have been identified and corrected--or understood by pilots who can allow for them.
So you just don't know.
It's always fun discussing whether you should measure safety by passenger miles, but I think it is. You have to get there somehow
. Some pilots used to make a point of announcing on landings that you would soon be on the most dangerous part of the trip, the drive home. Ha ha. Big laffs. But, I think, true.
P.S. I only have had one acquaintance--a very distant one--who has ever died on an airline flight. She was on American Airlines Flight 11 on September 11th, 2001. The plane was a a Boeing 767-223ER. The plane wasn't the problem.
Annual income twenty pounds, annual expenditure nineteen nineteen and six, result happiness; Annual income twenty pounds, annual expenditure twenty pounds ought and six, result misery.