PRAGUE, Oct 6 (Reuters) - Executives from Boeing ( BA )

and Airbus dampened speculation of imminent decisions

to replace their best-selling narrowbody models, telling a major

audience of investors that it would take time to achieve the

required jump in performance.

The Wall Street Journal reported last week that Boeing ( BA ) was

in the early stages of developing a 737 successor. But marketing

chief Darren Hulst told the International Society of Transport

Aircraft Trading that a launch is "some way off" while a senior

Airbus executive said it would "take a bit of time" to achieve

the 25-30% efficiency gain needed to attract the market.

Both executives were speaking in response to questions on

stage during an ISTAT gathering in Prague.

(Reporting by Tim Hepher; Editing by Emelia Sithole-Matarise)