COVID-19 PANDEMIC (Details) $ in Millions	1 Months Ended	3 Months Ended
	May 14, 2020 aircraft	Mar. 31, 2020 USD ($) aircraft
Impaired Long-Lived Assets [Line Items]
Asset Impairment Charges		$ 145.0
Number of Mainline Aircraft Parked | aircraft		146
Impairment of Intangible Assets, Finite-lived		$ 10.0
Accounts Receivable, Allowance for Credit Loss, Writeoff		$ 5.0
Number of Mainline Aircraft Parked | aircraft		146
Number of Horizon Aircraft Parked | aircraft		13
Number of SkyWest Aircraft Suspended | aircraft		8
Subsequent Event [Member]
Impaired Long-Lived Assets [Line Items]
Number of Mainline Aircraft Parked | aircraft	10
Number of Mainline Aircraft Parked | aircraft	10
Aircraft [Member]
Impaired Long-Lived Assets [Line Items]
Asset Impairment Charges		$ 69.0
Operating Lease Asset
Impaired Long-Lived Assets [Line Items]
Asset Impairment Charges		62.0
Disposal Group, Held-for-sale, Not Discontinued Operations
Impaired Long-Lived Assets [Line Items]
Asset Impairment Charges		4.0
Inventories
Impaired Long-Lived Assets [Line Items]
Asset Impairment Charges		2.0
Lease Return Costs
Impaired Long-Lived Assets [Line Items]
Asset Impairment Charges		8.0
Airbus [Member]
Impaired Long-Lived Assets [Line Items]
Asset Impairment Charges		$ 83.0
Aircraft Permanently Parked | aircraft		12
Aircraft Permanently Parked | aircraft		12
Airbus [Member] | Aircraft [Member]
Impaired Long-Lived Assets [Line Items]
Asset Impairment Charges		$ 11.0
Airbus [Member] | Operating Lease Asset
Impaired Long-Lived Assets [Line Items]
Asset Impairment Charges		62.0
Airbus [Member] | Disposal Group, Held-for-sale, Not Discontinued Operations
Impaired Long-Lived Assets [Line Items]
Asset Impairment Charges		0.0
Airbus [Member] | Inventories
Impaired Long-Lived Assets [Line Items]
Asset Impairment Charges		2.0
Airbus [Member] | Lease Return Costs
Impaired Long-Lived Assets [Line Items]
Asset Impairment Charges		8.0
Q400 [Member]
Impaired Long-Lived Assets [Line Items]
Asset Impairment Charges		$ 62.0
Aircraft Permanently Parked | aircraft		2
Aircraft Permanently Parked | aircraft		2
Q400 [Member] | Aircraft [Member]
Impaired Long-Lived Assets [Line Items]
Asset Impairment Charges		$ 58.0
Q400 [Member] | Operating Lease Asset
Impaired Long-Lived Assets [Line Items]
Asset Impairment Charges		0.0
Q400 [Member] | Disposal Group, Held-for-sale, Not Discontinued Operations
Impaired Long-Lived Assets [Line Items]
Asset Impairment Charges		4.0
Q400 [Member] | Inventories
Impaired Long-Lived Assets [Line Items]
Asset Impairment Charges		0.0
Q400 [Member] | Lease Return Costs
Impaired Long-Lived Assets [Line Items]
Asset Impairment Charges		$ 0.0