You are using the wrong analogy. Modern cars are NOT tested like they used to. When Peugeot wanted to test their cars, they'd simply drive them from France to Senegal and see what broke down. That's how Paris-Dakkar Rally was born. And that's why French cars would lose all plastic panels in the first two years but would then go on forever. Mercedes would run their engines till they broke down and saw where and how it broke.
These days, testing is done "in a more scientific way". Car manufacturers are NOT "looking for the worst conditions possible". They send several prototypes to "testing grounds", in Rovaniemi for winter testing, in South Africa or Mohave Desert for high-temperature runs, and to their "proving grounds" in Indonesia and Malaysia for "humid climate tests". Once there, they have meticulously laid out "courses" with strictly measured bumps and cracks, strictly defined "cycles" each car should drive on each stretch of track, etc. Kontuirlicher Verbesserungprocess. Of course, as any "scientific" testing, it has to be verifiable, recordable and repeatable, which by definition cannot model every life situation the car will meet on the road. Cars are simply no longer tested to destruction.
Now as for the airplanes, I have NO idea how those two are connected because by definition every flight or service of an airplane is, in theory at least, verifiable, recordable and repeatable, i.e. absolutely identical.