There's been some discussion of late around here on the apparent decline of aircraft useful lives. Boeing has weighed in with an extensive study and released a summary of its findings. A summary of the summary is summed up in this excerpt:
[F]leet evolutions of the current-generation of airplanes, such as the Next Generation 737 and A320, are following the same trend as previous generations of airplanes. Boeing has found no evidence of a meaningful change in airplane economic life over the last two decades, or going forward.
A key chart from Boeing's document appears below. It depicts the percentage of a given fleet remaining in service over time and the total fleet's average age, including airframes in service, parked, and scrapped.
Boeing's analysis of every western-built jet delivered through 2012 (all 31,032 of them) shows that 737NG and A320 retirement patterns are similar to the 727s and original 737s and not too far off of the 757 and MD80/90 family.
Comparing average retirement ages of a current, partially retired fleet and a more advanced fleet with a higher percentage of parked planes skews the data, Boeing says. Such efforts pit what are typically the least efficient airframes--the earliest delivered--against an entire, mature fleet flush with upgrades that has more completely run its course.
Boeing promises more detail--and some hard data--in an upcoming technical paper based on the study. Stay tuned.