The new Air Force One, which President Trump flew on earlier this week to Turkey, lacks the same defensive countermeasures that were security features of the old model, including its advanced antimissile capabilities, according to multiple officials who have been briefed on how the jet was retrofitted.Experts say the absence of those capabilities on the Boeing 747-8 aircraft, which was donated by Qatar, creates potential risk in using the jet abroad, a dynamic underscored by the abrupt decision on Wednesday for Mr. Trump to leave Turkey on the old Air Force One at the urging of the Secret Service.The episode...