Samsung Electronics Co Ltd unveiled its latest Galaxy S smartphones featuring a slim body made from aircraft-grade metal, in a bid to reclaim its throne as undisputed global smartphone leader from Apple Inc. Designed from scratch in an operation dubbed "Project Zero", the Galaxy S6 and its curved-edges variant are critical for Samsung's plans to reverse plunging smartphone revenues that led to its first annual earnings fall in three years in 2014. By some estimates, Apple surpassed Samsung as the world's biggest smartphone maker late last year, selling a record 74.5 million iPhones in the December quarter on the back of the success of its big-screen iPhone 6 and 6 Plus.