Boeing has revised plane's performance specifications

     Boeing updated the technical specifications of its jetliners to reflect the way airlines use them and also the trend toward heavier passengers, seats and cargo. The world's biggest plane maker stressed that the airplanes themselves have not changed. Instead, the specifications were altered a few days ago to better reflect their actual performance, a shift industry experts called long overdue.

Boeing increased the seat count on its main widebody planes, the 787 and 777, which makes the cost per seat lower for airlines. Seat counts for the narrow-body 737s remain unchanged. Boeing cut the range for all of the planes, with the recently introduced 787-9 falling the most, by 665 nautical miles (1,230 km).

Those changes reflect the fact that the new premium seats, often lie-flat beds, are about 100 pounds heavier than in the past. Assumptions for passenger and luggage weights also are higher, but Boeing declined to say what assumptions it uses.

"That weight gain, coupled in a slight uptick in the average weight that airlines allocate for passengers and their luggage, means we’ve made slight adjustments in the average range figures for our products: about 600 nautical miles less on average for twin-aisle airplanes, and 100 or so nautical miles less for our single-aisles", says Boeing.

The larger seating capacity on its widebody jets was not an effort to show better operating economics, the company said.

Rather it reflects the fact that many airlines are flying with two-class configurations in widebody planes, rather than three-class.

However, industry sources said decisions about standard seat counts can give broad clues to the way planemakers want their products to be perceived by airlines and lessors.

Boeing's changes were first reported by industry publication Flightglobal. They come after Europe's Airbus made similar revisions to its aircraft performance figures, also showing more seats on some of its widebody jets. Under the new measurements, Boeing's biggest plane, 747-8, is no longer its largest in terms of standard capacity.