Boeing has finally acknowledged increased interest in the proposed stretched 787-10 and says it will "probably happen".

The double-stretch of the baseline 787-8, first revealed by Flight International (20-26 September, 2005), is provisionally expected to seat up to 300 passengers in a tri-class layout, "plus or minus 10 or so", says 787 vice-president and general manager Mike Bair, who describes the development as a "relatively modest investment".

Bair also acknowledges the driving force behind the -10, which would compete head-on with the Airbus A350-900, comes from Dubai-based Emirates Airlines. "You've got to give credit to Emirates. They've been all over us to make us understand this, and its becoming fairly obvious that this was something that probably will happen," he adds. At an estimated 68m (223ft) in length, the 787-10 is sketched out to be around 6m longer than the 787-9, and would compete with Boeing's own 777-200ER.

Up until now this has made Boeing reluctant to seriously consider the -10, but the company now appears to be changing its mind given Emirates' insistence, growing interest from other carriers such as Qantas, and the imminent danger of the A350-900. Although Bair says it "could not really happen with an entry into service before 2012, but some time after that", the overall message is the -10 is now an accepted derivative option.

As for cannibalising the 777 market, Bair says: "It is better for us to step on [the 777] than someone else. If you can do a product that the market is clamouring for you'd be silly to ignore it."

Boeing is also increasing its market forecast for the medium twin sector from 3,300-3,500 to around 4,000 aircraft over the next 20 years.

"We'll get 50% of that at least, and if you do the maths, and see what the running average is, you can see what the rate has to be and we have to do better than that to protect the peaks."

To meet the market demand, Boeing has found slots for a further 16 aircraft at the end of 2009, which would bring deliveries to 112 aircraft for the first two years of production.