Spirit Airlines has finalised its firm order for 75 Airbus single-aisles including 45 A320neo aircraft.

The airline has yet to unveil its engine selection.

Spirit’s order for 45 A320 neo aircraft was booked in December 2011. The firming up of the additional 30 A320s in January brings the total new firm order to 75.

“For seven years we have been very successfully flying the A320 Family,” said Ben Baldanza, president of Spirit Airlines.

“The aircraft have been successful from every perspective – economy, environmental impact, comfort and efficiency. With more A320s and now the A320neo on their way to Spirit, we look forward to building on all the positives we’ve experienced so far.”

The new aircraft will be used on Spirit’s growing network of flights in the domestic United States, Caribbean and Latin America.

The A320neo is a new engine option for the A320 Family entering service from 2015 and incorporates latest generation engines and large Sharklet wing tip devices, which Airbus says will together deliver 15 per cent in fuel savings.

This reduction in fuel burn is equivalent to 1.4m liters of fuel – the consumption of 1,000 mid-size cars.

This saves 3,600 metric tons of C02 per aircraft per year, the amount absorbed by 240,000 mature trees.

The A320neo has over 95 per cent airframe commonality making it an easy fit into existing fleets while offering up to 500 nautical miles (950 kilometres) more range or two tonnes more payload at a given range.