SEOUL/NEW DELHI (Reuters) -South Korea is preparing to order all airlines in the country that operate Boeing jets to examine the fuel switches at the centre of an investigation into a deadly Air India crash that killed 260 people. Fuel switch locks have come under scrutiny after a 2018 advisory from the U.S. Federal Aviation Administration (FAA) figured in a preliminary report into last month's crash of Air India's Boeing 787-8 jet. Boeing referred Reuters' questions to the FAA, which was not immediately available to comment outside regular hours.