JetBlue Airways, which just unveiled the first Airbus A320 retrofitted with “sharklet” wingtips, still is negotiating terms with the airframer for retrofitting most of the rest of its fleet, Chief Operating Officer Rob Maruster says.

The New York-based low-cost carrier wants to determine how many work hours will be required to retrofit the A320s and how many spares it will need to keep on hand. Those factors are key in negotiating the cost, Maruster told Aviation Week after an unveiling of the first sharklet-enhanced aircraft at New York John F. Kennedy International Airport.

The first five JetBlue A320s receiving sharklets this year were recent deliveries that have sufficient support in the wing for the curved extensions to be bolted on—a procedure that JetBlue is doing in-house in less than two days per aircraft.

But for older aircraft in the fleet the work is more complicated and will be contracted out to a maintenance, repair and overhaul (MRO) provider. The wings cannot bear the weight and will need an extensive retrofit to accept the devices. Right now, JetBlue estimates the work will take 14-21 days, but it is working on a better estimate and signing a deal with an MRO facility later this year.

Whatever the final cost, the carrier says the fuel savings and other efficiency gains are more than adequate compensation. New A320s and A321s arriving this year will have line-fitted sharklets. The additions, which extend the wing by about 3 ft. and curve up another 8 ft., reduce drag and increase lift. The first sharklet-equipped aircraft, which was scheduled to begin service the weekend of Feb. 23, is expected to reduce fuel burn enough to save $568.75 on the flight from Kennedy to San Francisco International Airport. Over the course of a year, JetBlue says, the savings for one aircraft could amount to $350,000.

If the entire fleet were sharklet-equipped, annual savings could reach $45 million, the airline says. It also would avoid the stops the A320s currently must make to load more fuel to counter heavy headwinds on transcontinental flights. The sharklets boost range by 100 nm or payload by up to 1,000 lb.

The advantages, however, do not necessarily make the cost-benefit decision on using sharklets an easy one. Maruster says the benefits outweigh the costs for JetBlue because its average stage length is about 1,200 mi.

JetBlue also researched how the longer wing span would affect its airport operations when two of the aircraft are side by side, and found that only 10 of its gates are significantly affected. The airline has implemented special procedures for those gates.