Aircraft accidents are very rarely caused solely by technical failure.
Training and currency are by far the most important factors for safe flight , whether you are in a DC-3 or a B-787.
Pilots and maintenance personnel are the most vigorously tested and controlled specialist workers in just about any industry you can think of and the aviation record is second to none when you consider how many aircraft are in the air at any one time.
I've been in the industry for over 40 years and, when I'm a passenger, half the time I have to look in the seat pocket safety card to find out what type of plane I'm on as coming in through the finger dock,plane door and sitting down is not much different from BA to Boondock Airlines. (You can tell a National, or 'Prestige' airline quickly by the age and decrepitude of the cabin crew).
I pay far more attention to the company operating the aircraft than it's age or cycle life.
If it's old and still flying, they must have made a good one!
Some of the 'newer' planes in regular service that you fly in could well have far more work under their belt than these old '9s for all you know and could well be carrying far more squawks than them as well.Newer planes are much more complex and in the search for economy have not always become safer, but easier to fly using the automatics, cutting out human factors and reducing training time. (Viz Asiana crash) and burning less fuel than a Zippo to cross the ocean.
This does not always mean safer, but the record shows that flying is the safest form of transport, still.
There are folks here that say they won't climb on a particular plane, about which they know nothing, but will put their kids and loved ones on an un -maintained,Cheap, Chinese-made, underpowered, overloaded, brakeless motorbike , driven by a teen crack-head with no schooling and hurtle off into the homicidal traffic of SD or POP without aforethought!! Amazing
You'll never get me up on one of those things!!!!