"On March 24, 2022 we announced plans to accelerate our transition to a single mainline fleet, including plans to retire all Airbus A320 aircraft by early 2023 and our intent to phase out all A321 aircraft by the end of 2023, subject to agreement with counterparties. We also announced plans to transition to a single regional fleet, with all Q400 aircraft to be retired by the end of 2023. Subsequent to our announcement, certain fleet transition costs will be reported as special items. Such costs include impairment charges, lease return costs, and other incremental costs incurred as a consequence of the accelerated fleet transition."