Two more relatively young Boeing 737NGs arrived at a Wales-based part-out shop during the past weekend, evidently at the end of their service life, Aviation Week’s Fleets analysts report.

The aircraft, each just a shade under 15 years old, are among only 30 NG-model 737s to have retired so far. Many of those retired aircraft left the fleet when Malev of Hungary folded in February of 2012 and its fleet was liquidated.

The aircraft, which are believed to have gone to ECube Solutions, an “end-of-life” specialist based at the former RAF maintenance base at St. Athan, near Cardiff, were in service with JetLite until recently.

JetLite is a low-cost subsidiary of Jet Airways, which operates a mix of 737-700s, -800s and -900s.

The two JetLite aircraft, serial numbers 29043 and 29044, each have about 40,000 hr. and 30,000 cycles.

The aircraft are just the latest in a string of younger aircraft leaving active service early, a phenomenon driven by high demand for certain key parts—especially CFM International CFM56 engine components—and economic trends encouraging airlines to evaluate more upgauging.

As the pace of early retirements began to pick up in 2011, airline observers and particularly lessors began to consider whether the fundamental economic life assumptions on aircraft need to be rethought.

Boeing last month released a study contending that the retirements seen in recent years are “a blip,” and that while Airbus A320 and Boeing 737NG trends have shown up in the average retirement age, each aircraft type is trending like its predecessors’ 25-year average.

“Survival curves for Next Generation 737s and A320s are behaving like those of the previous generation,” Boeing says. “Although the Next Generation 737s and the A320s are still quite young fleets, their behavior, including a few retirements, are well within historical norms.”

So far, all the 737NGs that have retired have been -600s or -700s, and no -800s or -900s retirements have been reported to date.