EasyJet on Tuesday reached a new arrangement with Airbus giving the London Luton-based low-cost carrier additional flexibility in its existing fleet plan and the option to grow its fleet size by 2022 to 385 aircraft or reduce it to 316.

As part of the agreement, easyJet exercised purchase rights for 17 A320neos and is deferring the delivery dates of 18 A320neo aircraft by up to two years. These aircraft, the airline pointed out, are subject to a “very substantial discount” from the list price under a deal signed in July 2013, when it placed a firm order with the European OEM for 35 A320ceos and 100 A320neos, plus a further 100 A320neo purchase rights.

“In the [new] arrangement with Airbus we effectively pressed the re-start button on flexibility,” easyJet CFO Andrew Findley told analysts during the company’s full-year results presentation on Tuesday. The newly added flexibility comes on top of the “already significant flexibility” agreed in the original 2013 deal, he said. The airline can now defer deliveries of up to 30 aircraft between 2020 and 2022 “if we so wish.”

In addition, easyJet negotiated early lease returns and non-extension of existing leases.

Under its current fleet plan, easyJet is set to increase the number of aircraft to 329 Airbus narrowbodies in the current financial year through September 30, 2019, and to either 352 or 359 units in the 2020 financial year. Its total fleet at the end of September consisted of 315 aircraft, up from 279 aircraft a year earlier. The fleet now comprises 132 A319s, seventy-five 180-seat A320s, ninety-three 186-seat A320s, 13 A320neos, and two A321neos.

The LCC also converted purchase rights for 25 A320neos into options to secure “valuable” delivery slots in 2024, “when the Airbus order book has limited availability.”

Airbus said the firm order brings easyJet’s combined order for its single-aisle neo to 147, including 30 A321neos. The newly ordered A320neos are configured with 186 seats in a single-class configuration and powered by Leap CFM engines.