Originally Posted by
LarryJ
Transport jets, properly maintained, can have a long, productive life long after passing 25 or 30 years in service.
In 2011, I was flying DC8s that had been built as early as 1967. One of them is still flying today for Samaritan Purse (though I don't remember the manufacture date for that specific airplane).
If repaired, I would think that the lack of availability of replacements is a big factor. Also, when UA is finished with it, it will be in demand by the ACMI industry as a freighter.
I saw the Samaritan Purse DC-8 at OSH two years ago... pretty cool! At least with passenger jets, at airline levels of utilization, maintenance, especially HMV, becomes more expensive as the aircraft ages, and reliability suffers as well. Lower utilization patterns with freight flying can stretch those intervals out quite a bit, making it more economical.
30 years of service has traditionally been something of an inflection point for US carrier fleets, so it's notable (and fantastic, IMO) that UA appears committed to keeping a material portion of the fleet in service past that point, including conducting major structural repairs on its oldest frame.