Korean Air's order for six Airbus A330-200s makes it the first customer to commit to the higher-weight version of the twin-jet, unveiled by the airframer last year.
At 238t maximum take-off weight, the jet is about 5t heavier than the regular A330-200.
Airbus also claims that the aircraft will be able to operate over an extended range of 7,200nm (13,300km) - higher than the baseline figure of 6,800nm.
The company last year indicated that the higher-weight aircraft would compete for opportunities opened by delays to the Boeing 787 programme.
Airbus is making the new A330 available from 2010, the delivery date for Korean Air's aircraft. The Seoul-based carrier's agreement brings its total A330 order to 25.
Korean Air says the updated A330 variant is an "even more attractive option" for the airline and will allow it to open new long-haul services.