OPERATING SEGMENTS - Summary of financial information for the operating segments (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024
OPERATING SEGMENTS
Operating Revenues	$ 326,649	$ 311,483
Aircraft Fuel	64,619	70,304
Salaries, Wages, and Benefits	92,845	82,238
Maintenance	18,862	16,817
Sales and Marketing	10,395	10,679
Depreciation and Amortization	24,804	23,809
Ground Handling	11,407	9,154
Landing Fees and Airport Rent	16,833	14,729
Special Items, net	1,799	0
Other Operating, net	28,839	28,577
Total Operating Expenses	270,403	256,307
Operating Income	56,246	55,176
Interest Income	1,995	2,448
Interest Expense	(9,625)	(11,112)
Other, net	(478)	46
Income Before Income Tax	48,138	46,558
Passenger
OPERATING SEGMENTS
Operating Revenues	298,492	287,535
Aircraft Fuel	64,619	70,304
Salaries, Wages, and Benefits	75,183	65,588
Maintenance	15,343	13,404
Sales and Marketing	10,395	10,679
Depreciation and Amortization	24,799	23,804
Ground Handling	11,407	9,145
Landing Fees and Airport Rent	16,684	14,576
Special Items, net	1,799	0
Other Operating, net	23,543	23,504
Total Operating Expenses	243,772	231,004
Operating Income	54,720	56,531
Cargo
OPERATING SEGMENTS
Operating Revenues	28,157	23,948
Aircraft Fuel	0	0
Salaries, Wages, and Benefits	17,662	16,650
Maintenance	3,519	3,413
Sales and Marketing	0	0
Depreciation and Amortization	5	5
Ground Handling	0	9
Landing Fees and Airport Rent	149	153
Special Items, net	0	0
Other Operating, net	5,296	5,073
Total Operating Expenses	26,631	25,303
Operating Income	$ 1,526	$ (1,355)