Suspense over the appearance of America’s newest combat jet, a diplomatic chill between the West and Russia and the re-launch of an Airbus jet with a surprise tweak in its name could make the Farnborough Airshow one of the least predictable for years. While the world’s largest aerospace event is traditionally a cauldron for new technology and dazzling flying displays, technical problems forced the F-35 Joint Strike Fighter to withdraw from a warm-up event and Farnborough’s aircraft list is already crossed through with several high-profile no-shows.