Ryanair deputy chief executive Howard Millar believes Airbus' decision to launch the A320NEO has "put the ball right into Boeing's court".
From 2016 Airbus is planning to offer a re-engined Airbus A320, with two powerplant options: the CFM Leap-X or Pratt & Whitney's PW1100G.
Millar describes this as a "very interesting development", but he believes the timeframe is "lengthy" and that the money would be better spent on an all-new successor rather than an intermediate step.
"We feel that, on a longer-term basis, the investment in upgrading aircraft would be better spent on the development of a totally new generation of aircraft," said Millar, speaking to ATI at Ryanair's Dublin headquarters.
"That way we can incorporate the latest developments in composite and engine technology, so we get a plane which really delivers very significant cost savings, but also places us well in terms of technology for 2020 and beyond."
With Airbus still busy with both the A380 and A350 XWB programmes, and Boeing tied up with its 787 and upgrades to the 777, Millar voices concerns about Airbus' ability to deliver the A320NEO within its proposed 2016 timeframe.
"I think the market would be generally concerned about the manufacturer's ability to deliver the aircraft on time, given recent performance [from both Boeing and Airbus]," he explains.
"We think this is an awful lot to ask the manufacturers to deliver in this time period and to us, as an outsider, it looks very aggressive."
Millar adds that Boeing is not expected to come back with a clean sheet response until "at least 2020", although the US manufacturer must deal with complications because existing 737s have less ground clearance than the A320. Even with this hurdle, Millar believes Airbus has "put the ball right into Boeing's court".
"We think they should go for a new aircraft. Don't spend any more money on the 737, just make it more cheaply," urges Millar.