Engine technology is absolutely key to determining when and with what Airbus and Boeing replace their current top-selling narrowbody families.
When I started on Flight International in 2001, the big two were making noises about having all-new single-aisle jetliners on the market in the early years of this decade. Nine years on, we're arguably as far from flying in replacements for the A320 and 737 as we seemed to be then.
Of course, there have been two down cycles since then sparked by 9/11 and the global credit crunch. Programmes, from the A380 and A400M to the 787 and 747-8 have gone wrong, draining resources from both manufacturers.
But there are two main reasons that all-new narrowbodies have been delayed: the if-it-aint-broke factor (the A320 and 737 are still selling like hot cakes) and the engines factor (until the engine makers can deliver a step-change in performance, it is simply not worth Airbus or Boeing investing the billions required in designing new airframes).
In this week's issue we examine exactly where the aeroengine powerhouses are with their main contenders, the CFM Leap X and the geared turbofan from Pratt & Whitney, partner in CFM rival International Aero Engines. Are these the breakthroughs necessary to prompt either Airbus or Boeing to make the plunge, or does the technology still have some maturing to do?
Also in this issue, we report from the India Aviation show in Hyderabad, where the country's National Aerospace Laboratories revealed the configuration of its planned RTA-70 indigenous regional turboprop, and invited prospective international partners to take a look.
There's a story about the parts shortage plaguing the Joint Strike Fighter, something likely to prompt another delay to the troubled programme.
And Craig Hoyle reveals how the future of the Eurotraining project - which was aimed at procuring a joint aircraft and training system for military pilots in nine nations - is threatened. Have national politics and budgetary squabbling smothered an aspiration which, on paper at least, appeared to make sense?