Airbus is set to release refined performance expectations for the re-engined A320neo over the next few weeks as it moved closer to securing a formal launch order for the type.
Indian budget airline IndiGo has tentatively signed for 150 of the type - without indicating its crucial engine choice - through a memorandum of understanding that also includes 30 regular A320s.
Airbus is detailing its 2010 performance in Toulouse next week and says: "Now things are happening commercially, we're ready to talk about the specifications."
The airframer has been aiming for a 15% reduction in fuel-burn from the newer engines and improved aerodynamic performance from modifications such as the "sharklet" wingtips.
Data so far has indicated that the airframe for the A320neo - excluding engine assemblies - will be 250-300kg (550-660lb) heavier than the current A320, and that the maximum empty weight will depend on the engine selection. The CFM International Leap-X variant will be lighter by 100kg than the Pratt & Whitney PW1100G version.
The A320neo is due to come into service in 2016, when IndiGo expects to begin taking delivery of the newly developed twinjets. IndiGo is adamant that it will also take all the aircraft it has on order - a backlog of 61 A320s - in addition to the 180 featured in the potential launch deal.
Having regularly taken delivery of aircraft at around eight or nine a year since its first in 2006, IndiGo is to step up the acceptance rate. Fourteen will be added this year, and it will take all 61 outstanding A320s by 2015.
Low-cost carrier IndiGo had its beginnings in 2005, when it placed an order for 100 Airbus A320s at the Paris air show. The privately owned airline was founded by travel-related IT services firm InterGlobe Enterprises and former US Airways chief executive Rakesh Gangwal.
The airline had its first flight in August 2006 and operates 221 flights weekly, with 34 A320s, to 24 destinations in India.
It has the biggest market share among low-cost carriers in India. In November 2010 it was ranked third in terms of market share among all Indian airlines in the domestic market, coming in after Jet Airways and Kingfisher Airlines.