Qualified disagreement -- it's all about the word modern. The Comet airframe was inherently limited by the decision to embed the engines -- de Havilland Ghost

Qualified disagreement -- it's all about the word modern. The Comet airframe was inherently limited by the decision to embed the engines -- de Havilland Ghost turbojets -- in the wing roots. Obviously this wwas great for drag reduction, but it made it difficult to modify the design to accommodate other, more efficient/economical engines. In the end, the attempt to refit the last Comet-descended airframes, the RAF's Nimrod MRA2's to MRA4 spec with Rolls-Royce BR700 turbofans in the 1990s/2000s failed due to spiraling prices because the higher diameter turbofans required substantial redesign/reworking of the wing roots. More here: https://en.wikipedia.org/wiki/BAE_Systems_Nimrod_MRA4#Delays_and_development_problems https://en.wikipedia.org/wiki/BAE_Systems_Nimrod_MRA4#Delays... Now compare this to the succssful engine retrofit program for the USAF's KC-135 fleet, which kept them in service for a couple more decades: https://en.wikipedia.org/wiki/Boeing_KC-135_Stratotanker#Engine_retrofits https://en.wikipedia.org/wiki/Boeing_KC-135_Stratotanker#Eng... Having the engines hung on pods below the wing (or alongside the fuselage) makes them inherently easier to service and easier to upgrade (although problems can emerge if you push it too far, as witness the Boeing 737 MAX crashes). This isn't to dismiss the Comet completely: it was a pioneering design, broke ground, and was the first trans-Atlantic jet airliner in service. But it had design flaws beyond the infamous metal fatigue problem.