Comments by "Titanium Rain" (@ChucksSEADnDEAD) on "Buy your own air force! | Jeremy Clarkson's Extreme Machines | Top Gear" video.

This is somewhat misleading. The aircraft still works, but the problem is that the older it is the more maintenance it requires. Parts become harder to come by. Using them incurs a great cost. And at some point, the airframe reaches the limit. No more flight hours. It needs to stop or it risks breaking apart mid-air.
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@j4v-cyberpunk-music The issue is that aircraft need to keep weight down considering that they need to expend energy to stay aloft. So they're built as light as possible. They are sturdy. But they are rated to tens of thousands of hours, and as they approach the limit they start to require overhauls. You could design a stout aircraft that would last forever, but the performance would be terrible due to excess weight. Yes, typically welded constructions are considered to be physically one to simplify design considerations but welds are important stress concentration areas. Especially in aircraft, which have much more stringent control than most produced goods. If you create excessive load on a welded structure the weld is the most probable location for failure. Even disregarding the weld, a solid piece will fail with cyclic loading. It's called fatigue. Spare parts often cannot be produced continuously. For example Sikorsky has stated they will not support certain parts for some ANG Black Hawks because they were produced to too old of a standard. There's multiple, more modern variants of Black Hawks that they need to support and they cannot waste time and resources dedicated to limited runs of obsolete parts when they have so much on their plate. So the ANG has to take the schematics and contract a limited production run. This is expensive. If you reach a point there's too many parts that are being contracted out the only options are cannibalizing old airframes if they exist or just retire them. Imagine asking Intel to keep producing a Pentium 3. They'd refuse.
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