Stock Compensation	3 Months Ended
Mar. 28, 2024
Share-Based Payment Arrangement, Noncash Expense [Abstract]
Stock Compensation	Stock Compensation Holdings has established the stockholder-approved Amended and Restated 2014 Omnibus Incentive Plan (the “Omnibus Plan”), to grant cash and equity awards of Holdings’ Class A Common Stock, par value $0.01 per share (the “Common Stock”), to certain individuals. Holdings has established the Long-Term Incentive Plan (the “LTIP”) under the Omnibus Plan to grant equity awards to certain employees of the Company. The Company recognized a net total of $10.1 and $9.0 of stock compensation expense for the three months ended March 28, 2024 and March 30, 2023, respectively. During the three months ended March 28, 2024, 409,170 time or service-based restricted stock units (“RSUs”) were granted with an aggregate grant date fair value of $11.9 under the Company’s LTIP. Awards vest over a three-year period, beginning on the date of grant. Values for these awards are based on the value of Common Stock on the grant date. During the three months ended March 28, 2024, 388,386 performance-based restricted stock units (“PBRSUs”) were granted with an aggregate grant date fair value of $14.9 under the Company’s LTIP. These awards are earned based on Holdings’ total shareholder return relative to its peer group over a three-year performance period. Values for these awards are initially measured on the grant date using the estimated payout levels derived from a Monte Carlo valuation model. During the three months ended March 28, 2024, 384,734 shares of Common Stock with an aggregate grant date value of $16.0 vested under the Company’s LTIP. The Company maintains the Spirit AeroSystems Holdings, Inc. Employee Stock Purchase Plan (the “ESPP”) which became effective on October 1, 2017 and was amended and restated on October 21, 2022. Under the amended plan, the per-share purchase price for the Company’s Common stock purchased under the ESPP is 85% of the lower of (a) the fair market value of a share on the first day of the applicable offering period or (b) the fair market value of a share on the applicable purchase date. The Company recognized $0.7 of stock compensation expense related to the ESPP for the three months ended March 28, 2024. The Company recognized no stock compensation expense related to the ESPP for the three months ended March 30, 2023.

Holdings has established the stockholder-approved Amended and Restated 2014 Omnibus Incentive Plan (the “Omnibus Plan”), to grant cash and equity awards of Holdings’ Class A Common Stock, par value $0.01 per share (the “Common Stock”), to certain individuals. Holdings has established the Long-Term Incentive Plan (the “LTIP”) under the Omnibus Plan to grant equity awards to certain employees of the Company.

The Company recognized a net total of $10.1 and $9.0 of stock compensation expense for the three months ended March 28, 2024 and March 30, 2023, respectively.

During the three months ended March 28, 2024, 409,170 time or service-based restricted stock units (“RSUs”) were granted with an aggregate grant date fair value of $11.9 under the Company’s LTIP. Awards vest over a three-year period, beginning on the date of grant. Values for these awards are based on the value of Common Stock on the grant date.

During the three months ended March 28, 2024, 388,386 performance-based restricted stock units (“PBRSUs”) were granted with an aggregate grant date fair value of $14.9 under the Company’s LTIP. These awards are earned based on Holdings’ total shareholder return relative to its peer group over a three-year performance period. Values for these awards are initially measured on the grant date using the estimated payout levels derived from a Monte Carlo valuation model.

During the three months ended March 28, 2024, 384,734 shares of Common Stock with an aggregate grant date value of $16.0 vested under the Company’s LTIP.

The Company maintains the Spirit AeroSystems Holdings, Inc. Employee Stock Purchase Plan (the “ESPP”) which became effective on October 1, 2017 and was amended and restated on October 21, 2022. Under the amended plan, the per-share purchase price for the Company’s Common stock purchased under the ESPP is 85% of the lower of (a) the fair market value of a share on the first day of the applicable offering period or (b) the fair market value of a share on the applicable purchase date.

The Company recognized $0.7 of stock compensation expense related to the ESPP for the three months ended March 28, 2024. The Company recognized no stock compensation expense related to the ESPP for the three months ended March 30, 2023.