India approved its biggest defence deal with the US for 10 Boeing C-17 strategic heavy-lift planes for $4.1 billion, in a major step to augment the capability of its air force to swiftly move troops and equipment over long distances. The cabinet committee on security, at a meeting here chaired by Prime Minister Manmohan Singh, gave its nod for the deal to equip the Indian Air Force (IAF) with the aircraft. “The cabinet committee on security has approved the C-17 deal at an approximate cost of $4.1 billion,” a senior defence ministry official said.