Airbus is set to announce a partial redesign of the A330 at the Farnborough Airshow to boost the range of the wide-body passenger jet as Boeing ponders a new competing version of its 787 Dreamliner, industry sources said on Monday.

The move reflects an attempt to maintain the success of one of Airbus's most profitable aircraft after a second honeymoon in the market driven by delays to the Boeing carbon-fibre plane.

The A330 twinjet is a sister aircraft of the Airbus A340, a larger four-engine model whose production has now been halted.

Since the aircraft shared the same wing, the end of the A340 allows Airbus to clean up some of its features and increase the maximum amount of fuel or payload at take-off by two tonnes and in turn extend its range.

Airbus says the A330 is likely to sell well for some time but is sensitive to the way the changes are being marketed as Boeing trumpets a radical change in the lighter carbon 787.

The move to freshen up the A330 was originally code-named "A330 Ultimate" but the name has been axed to avoid creating any suggestion that the A330, in service since the 1990s, is nearing the end of its career.

The limited design changes confirm that Airbus has decided against a deeper overhaul for the A330 with new engines.

Airbus has enjoyed a second wave of sales for the A330 due to delays in deliveries of the Dreamliner and is keen to prolong the aircraft, whose development is paid for and which is a second important source of cash alongside the narrowbody A320.

Boeing is drawing up plans for a lighter-weight Dreamliner called the 787-10 seating 320 people that would in part compete with the 295-seat A330-300 but reach about 1,000 miles further.

It is one of two projects Boeing is working on to maintain a leadership over Airbus in long-distance twin-aisle jets, alongside an extensive redesign of the 777 mini-jumbo.

Boeing says it has not completed preliminary studies in the 787-10 but is likely to push ahead with it before the 777.

However in engineering terms the 787-10 would be a "double-stretch" - a stretch of the already stretched 787-9.

Analysts caution building such aircraft without too many compromises in performance as weights gets added is not easy as Boeing found with the 767-400, which did not sell well.

"The risk is that you add capacity but lose too much range," said Nick Cunningham of Agency Partners in London.

Airbus declined comment but said it had scheduled a product announcement for later on Monday.