When a person can retire young, it is a good thing, but the early retirement of aircraft has consequences for the aviation industry when it occurs in larger numbers, as is the case now for commercial jets.

For each year from 1997-2008, the average and median retirement age for commercial jets were in the 28-30-year range, aside from one dip in median age to 27 years in 2005, an Aviation Week analysis shows. But the retirement age dropped to an average of 26.5 and median of 24.8 in 2009, and has stayed lower in the years since.

It is taking another drop so far this year, with the average age down to 24.8 years and the median to 23.8 through mid-June. If those numbers hold, they would be the lowest since 1991.

Many of the retirees are Bombardier CRJ100/200 aircraft, now no longer financially viable on many routes, but Boeing 737 and Airbus A320 family jets also are contributing to the decline. Retired so far in 2012 before 15 years of age are: eight 737-600s, two A319-100s, an A320-200, an A321-200, an A320-200, two 747-400s and a 737-700.

The two 747-400s could be a harbinger of retirements to come; the more fuel-efficient 777-300ER has become a popular replacement.

A340-300s also are prime part-out candidates because of the number becoming available and a lack of secondary marketing opportunities, says Owen Geach, commercial director for the International Bureau of Aviation, a global, U.K.-based aviation consultancy and aircraft appraiser.

To be sure, some aircraft are retired due to special circumstances, such as the limited production and customer base with the 737-600, but there also are broader forces at work. Rising oil prices are making investments in newer, fuel-efficient aircraft more worthwhile. Long-time airline customers for aging aircraft—in China, Russia and Latin American and African countries—are confronting new government restrictions on the age of aircraft they can acquire. And the financial community is reluctant to fund older airplanes it does not want to be left holding.

For good or ill—depending on which side of the market an airline or company is on—all of this is having an impact on aircraft residual values, financing options, parts pricing, lease rates and more. There is a flip side to this: If the trend reverses, Airbus and Boeing could be left with aircraft overproduction. But barring a major decline in fuel prices, a reversal in the near term does not seem likely. Aircraft are retiring younger, and everyone in the aviation industry who is not fortunate enough to be able to do the same will need to adjust accordingly.