Airbus is seeing better than expected fuel-burn savings during initial flight trials of its A320 winglet upgrade.

The lift devices, which Airbus calls Sharklets, are supposed to replace wing-tip fences on A320s starting this year and on all NEO narrowbodies when the re-engined aircraft enter service starting in 2015.

Flight testing of a modified A320 (MSN1) began in late 2011 with the first A320 equipped with the devices as a forward fit (MSN5098) completing its first flight in April.

The certification phase of the program is expected to total 600 hours

Early indications are the fuel-burn savings may exceed estimates, says Fernando Alonso, senior VP for flight and integration tests at Airbus. The aircraft maker was hoping to see an improvement in fuel burn of up to 3.5% on long flights.

Low-speed performance of the A320 is not degraded by the addition of the winglets and, according to Alonso, handling standards—which can be affected by these wing tips—are being maintained.

So far only A320s are flying within the winglets, although Airbus intends on introducing the modification on its entire single-aisle product range.