WASHINGTON—Aircraft parts manufacturer Spirit AeroSystems said on Wednesday it is mandating COVID-19 vaccines for its 10,500 employees by Dec. 8 in line with an executive order for contractors signed by U.S. President Joe Biden last month. The White House announced the Dec. 8 deadline for employees of federal contractors and the requirements are expected to cover millions of employees. “As a federal contractor, testing is not an option for Spirit employees,” the Wichita, Kansas-based company said. Last month, Raytheon also said it would require all U.S. employees to be vaccinated, while Southwest Airlines, which also has significant federal contracts, said Monday it would require its U.S. employees to be vaccinated by Dec. 8. The White House is adding clauses to future government contracts mandating inoculations. An administration official told Reuters last month the White House was interpreting the vaccination requirements for contractors “broadly,” saying they extend beyond those who work …