UPDATE 1-Airbus offers to retrofit fuel-saving A320 wingtips
* JetBlue deal marks 10,000th order for A320-family aircraft
* Airbus says "sharklet" wingtips cut fuel by up to 4 pct
PARIS, Oct 29 (Reuters) - European planemaker Airbus announced plans on Tuesday to retrofit fuel-saving wingtips on older versions of its A320 jets as sales of its best-selling aircraft hit 10,000.
The move will see upward-slanted wingtips, which have become an increasingly common sight on new aircraft, become available for A320-family jets already in service.
Planemakers are battling wingtip to wingtip to squeeze improvements out of the designs of their most popular models by introducing new and more aerodynamic shapes to save fuel.
By bending and even splitting wingtips, planemakers can reduce drag and create more lift, reducing the consumption of fuel, which is one of the airline industry's biggest costs.
Airbus says the slanted wingtips, which it calls sharklets, will cut fuel costs by up to 4 percent and increase range by up to 100 nautical miles (185 kilometers).
The wingtip devices are already available on newly sold A320-family jets and an upcoming version boasting new engines, due in late 2015, but Airbus is now matching Boeing in making them available on older models as an option.
Boeing also installs curved wingtips on its competing 737 jets and has come up with an open-jawed design for the next version of the plane, the 737 MAX.
The design, with the wing split at the end and angled both upwards and downwards, will become a familiar sight in airports from 2017 when the 737 MAX is due to enter service.
Boeing said on Tuesday it had managed to eke out a further 1 percent in fuel savings for the 737 MAX, compared with the existing model of 737, bringing the total gain to 14 percent.
Airbus and Boeing have a roughly equal split of the market for narrowbody, medium-haul jets seating around 150 people and each plans to bring out upgraded versions around mid-decade.
Airbus said on Tuesday it had reached the 10,000th order for A320-family aircraft thanks to a deal with JetBlue Airways for 35 additional planes.