Spirit AeroSystems second quarter of 2021 revenue was US$1.0 billion, up 55% from the same period in 2020, primarily due to higher production deliveries on the Boeing 737 and Airbus A320 programs and increased revenue from the recently acquired A220 wing and Bombardier programs. These increases were partially offset by the lower wide-body production rates due to reduced international air traffic resulting from the impacts of COVID-19. Deliveries increased to 243 shipsets during the second quarter of 2021 compared to 159 shipsets in the same period of 2020, including Boeing 737 deliveries of 35 shipsets compared to 19 shipsets in the same period of the prior year.
Spirit’s backlog at the end of the second quarter of 2021 was approximately US$34 billion, with work packages on all commercial platforms in the Boeing and Airbus backlog.
Operating loss for the second quarter of 2021 was US$97.7 million, as compared to an operating loss of US$367.0 million in the same period of 2020. The decreased loss was primarily driven by lower forward loss charges, lower costs related to excess capacity and lower losses on disposal of assets in the second quarter of 2021 compared to the second quarter of 2020. Second-quarter 2021 earnings included US$47.5 million of excess capacity costs and US$9.9 million of favorable cumulative catch-up adjustments. Additionally, the second quarter of 2021 included net forward loss charges of US$52.2 million, primarily driven by Boeing 787 engineering analysis and rework. In comparison, during the second quarter of 2020, Spirit recorded US$194.1 million of net forward loss charges, excess capacity costs of US$82.8 million and US$37.7 million of unfavorable cumulative catch-up adjustments. Additionally, during the second quarter of 2020, Spirit recognized loss on disposal charges of US$22.9 million related to certain long lived assets on the Boeing 787 and Airbus A350 programs.
Other income for the second quarter of 2021 was US$31.1 million, compared to a net expense of US$6.4 million for the same period in the prior year. The increase primarily reflects income related to the Belfast pension plan during the second quarter of 2021, as well as a non-cash expense of US$14.7 million recognized in the second quarter of 2020 resulting from the voluntary retirement program (VRP) offered during 2020 that did not recur in 2021.