The Boeing 747-8 being offered to U.S. President Donald Trump by Qatar once served the Qatari royal family and has been sitting unsold for years. The jet, a lavishly configured version of Boeing's largest passenger aircraft, has been lingering without a buyer since being put up for sale in 2020, according to aircraft listings and aviation analysts. Trump has publicly expressed frustration with Boeing's yearslong delay in delivering two modified 747s for presidential use. The president has argued that by accepting Qatar's offer, he can bypass delays and save U.S. taxpayers money. Critics, however, fear that the acceptance would be...