(3) Long-term Debt

Long-term debt consisted of the following as of December 31, 2014 and 2013 (in thousands):

	December 31, 2014			December 31, 2013
Notes payable to banks, due in semi-annual installments, variable interest based on LIBOR, or with interest rates ranging from 1.34% to 2.55% through 2015 to 2020, secured by aircraft	$	174,159		$	224,915
Notes payable to a financing company, due in semi-annual installments, variable interest based on LIBOR, or with interest rates ranging from 0.70% to 2.36% through 2015 to 2021, secured by aircraft		350,177			392,660
Notes payable to banks, due in semi-annual installments plus interest at 6.06% to 7.18% through 2021, secured by aircraft		129,201			149,477
Notes payable to a financing company, due in semi-annual installments plus interest at 5.78% to 6.23% through 2019, secured by aircraft		25,090			32,528
Notes payable to banks, due in monthly installments plus interest of 3.15% to 8.18% through 2025, secured by aircraft		572,446			623,315
Notes payable to banks, due in semi-annual installments, plus interest at 6.05% through 2020, secured by aircraft		13,551			15,740
Notes payable to banks, due in monthly installments, plus interest at 3.10% through 2019, secured by aircraft		5,909			—
Notes payable to banks, due in quarterly installments, LIBOR plus interest at 2.39% through 2029, secured by aircraft		378,406			—
Notes payable to banks, due in quarterly installments, plus interest at 3.8% to 4.0% through 2029, secured by aircraft		68,318			—
Notes payable to banks, due in monthly installments, interest based on LIBOR plus interest at 2.00% to 4.00% through 2016		28,554			31,933

Long-term debt	$	1,745,811		$	1,470,568


Less current maturities		(211,821	)		(177,389	)


Long-term debt, net of current maturities	$	1,533,990		$	1,293,179

During the year ended December 31, 2014, the Company acquired 20 new E175 aircraft and one used CRJ700 aircraft through the issuance of debt.

As of December 31, 2014, the Company had $1.7 billion of long-term debt obligations related to the acquisition of CRJ200, CRJ700, CRJ900 and E175 aircraft. The average effective interest rate on the debt related to those long-term debt obligations was approximately 4.1% at December 31, 2014.

The aggregate amounts of principal maturities of long-term debt as of December 31, 2014 were as follows (in thousands):

2015	$	211,821
2016		216,340
2017		190,648
2018		168,769
2019		161,329
Thereafter		796,904

	$	1,745,811

As of December 31, 2014 and 2013, SkyWest Airlines had a $25 million line of credit. As of December 31, 2014 and 2013, SkyWest Airlines had no amount outstanding under the facility. The facility expires on March 31, 2015 and has a variable interest rate of Libor plus 3.0%.

As of December 31, 2014 and 2013, the Company had $79.9 million and $88.5 million, respectively, in letters of credit and surety bonds outstanding with various banks and surety institutions.