PROPERTY AND EQUIPMENT - Schedule of Property and Equipment (Details) - USD ($) $ in Millions	Dec. 31, 2025	Dec. 31, 2024
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 3,793.3	$ 3,368.2
Less accumulated depreciation and amortization	(1,383.3)	(1,258.7)
Property and equipment, net	2,410.0	2,109.5
Aircraft
Property, Plant and Equipment [Line Items]
Total property and equipment	3,206.6	2,898.7
Engines and flight equipment
Property, Plant and Equipment [Line Items]
Total property and equipment	300.4	243.4
Land and buildings
Property, Plant and Equipment [Line Items]
Total property and equipment	211.3	158.9
Office equipment and leasehold improvements
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 75.0	$ 67.2