US-based Spirit Airlines and Airbus on Tuesday signed a Memorandum of Understanding for 75 aircraft of the A320 family worth $6.7 billion at list price. The commitment comprises 45 units of the fuel-efficient A320neo jetliner and 30 A320s, the two entities said at the signing ceremony. \"We are excited to expand our partnership with Airbus and grow into our next decade,\" said Ben Baldanza, chief executive officer of the Florida-based carrier. The new aircraft will be used on Spirit\'s targeted market in the United States, Caribbean and Latin America, an Airbus statement said. The agreement is expected to be firmed up before the end of the year, Airbus commercial director John Leahy said. The planes should be delivered between 2016 and 2021.