Boeing Chief Executive James McNerney shrugged off Airbus's plans to revamp its mid-sized A350 plane on Tuesday, calling it an "ambitious" attempt to counter the US planemaker's strong-selling 787 and 777 models.

Airbus stole the limelight at the Farnborough International Airshow on Monday with a USD$10 billion redesign of the A350 aimed at seizing back orders in the lucrative market for mid-sized jets, but Boeing is still beating its European rival in orders this year.

"They (Airbus) have come up with a concept that is ambitious... to secure that span with one family," McNerney said on the sidelines of the UK air show. "Short of just doing two new aircraft families I'm not sure what else they could do."

Amid delays on its A380 superjumbo and indecision over the A350, Airbus has fallen well behind Boeing in the race for new orders this year. Having outsold Boeing for the past five years, Airbus trailed 4-to-1 in the first six months of this year.

"It's too early to say," if Airbus was back in a position to compete, said McNerney, but he gave no indication of concern. "I don't feel any less comfortable about our position today than I did the day before yesterday," he said.

Airbus unveiled the A350 XWB (extra wide body) on Monday, in an attempt to answer complaints from key customers that the original A350 was narrower and less economical than Boeing's newest mid-sized models.

Airbus was still some way from offering a finished design to customers, McNerney said.

"The definition of the (A350) plane is really not anywhere near concrete. If you read between the lines, they still have months to go before they can get a concrete definition or even put parameters around what they can offer in comparison to us."

"It's a time-honored approach to try to get between two big successful airplane families by establishing a niche," said McNerney, referring to Boeing's 787 and 777 lines. "I don't want to judge, but it's a very ambitious strategy."