(9) Retirement Plans and Employee Stock Purchase Plans

SkyWest Retirement Plan

The Company sponsors the SkyWest, Inc. Employees’ Retirement Plan (the “SkyWest Plan”). Employees who have completed 90 days of service and are at least 18 years of age are eligible for participation in the SkyWest Plan. Employees may elect to make contributions to the SkyWest Plan. Generally, the Company matches 100% of such contributions up to levels ranging from 2% to 12% of compensation, based on position and years of service. Additionally, a discretionary contribution may be made by the Company. The Company’s combined contributions to the SkyWest Plan were $35.6 million, $26.1 million and $23.2 million for the years ended December 31, 2018, 2017 and 2016, respectively.

ExpressJet and Atlantic Southeast Retirement Plans

ExpressJet (formerly Atlantic Southeast) sponsors the Atlantic Southeast Airlines, Inc. Investment Savings Plan (the “Atlantic Southeast Plan”). Employees who have completed 90 days of service and are 18 years of age are eligible for participation in the Atlantic Southeast Plan. Employees may elect to make contributions to the Atlantic Southeast Plan, ExpressJet will match up to 6% of each participant’s total compensation, based on years of service and other provisions included in the Atlantic Southeast Plan. Additionally, participants are 100% vested in their elective deferrals and rollover amounts in company matching contributions.

ExpressJet additionally sponsors the ExpressJet Airlines, Inc. 401(k) Savings Plan (the “ExpressJet Retirement Plan”). Substantially all of ExpressJet’s domestic employees were covered by this plan at the time the Company acquired ExpressJet in 2010. Effective January 1, 2009, the ExpressJet Retirement Plan was amended such that certain matching payment amounts have been reduced or eliminated depending on the terms of the collective bargaining unit or work group, as applicable.

ExpressJet’s contribution to the Atlantic Southeast and the ExpressJet Retirement Plans was $15.4 million, $17.8 million and $21.0 million for the years ended December 31, 2018, 2017 and 2016, respectively.

Employee Stock Purchase Plans

In May 2009, the Company’s Board of Directors approved the SkyWest, Inc. 2009 Employee Stock Purchase Plan (the “2009 Stock Purchase Plan”). All employees who have completed 90 days of employment with the Company or one of its subsidiaries are eligible to participate in the 2009 Stock Purchase Plan, except employees who own five percent or more of the Company’s common stock. The 2009 Stock Purchase Plan enables employees to purchase shares of the Company’s common stock at a five percent discount, through payroll deductions. Employees can contribute up to 15% of their base pay, not to exceed $25,000 each calendar year, for the purchase of shares. Shares are purchased semi-annually at a five percent discount based on the end of the period price. Employees can terminate their participation in the 2009 Stock Purchase Plan at any time upon written notice.

The following table summarizes purchases made under the 2009 Employee Stock Purchase Plans during the years ended December 31, 2018, 2017 and 2016:


	Year ended December 31,
	2018		2017		2016
Number of shares purchased		60,950		88,362		151,531
Average price of shares purchased	$	49.85	$	33.96	$	20.87

The 2009 Stock Purchase Plan is a non‑compensatory plan under the accounting guidance. Therefore, no compensation expense was recorded for the years ended December 31, 2018, 2017 and 2016.