MIAMI — Las Vegas-based Allegiant Air has signed a purchase agreement for 12 Airbus A320 aircraft, the first order ever placed by the low-cost airline to any manufacturer.

The order, valued at 1.18 billion at list prices before customary discounts, comes a day after the carrier ratified a five-year agreement with its pilots, represented by the International Brotherhood of Teamsters (IBT).

“As we continue to transition to an all-Airbus fleet, this purchase will allow us to accelerate that process, reduce complexity in our fleet and provide our passengers with an ever-improving experience” said Maury Gallagher, Chairman and CEO of Allegiant Travel Company.

The aircraft ordered today correspond to the current engine (ceo) option, and will be powered by CFM56 engines from CFM International. These jetliners are expected to enter into service between 2017 and 2018.

“This purchase agreement is an important step in transitioning to a single fleet type,” said Jude Bricker, Allegiant chief operating officer. “Streamlining our fleet will increase efficiency across our entire operation and bring economic advantages in fuel savings and a higher number of seats — allowing us to continue offering the industry’s most affordable fares, while increasing reliability.”

With this acquisition, Allegiant now has 77 Airbus aircraft either in service or under contract for future delivery, taking a step further to the planned goal to have between 90 and 100 aircraft in service by mid-2019 as the carrier progressively phases out its McDonnell Douglas MD-80s, with the last leaving the fleet by the fall of 2020.