A heat exchanger system for a gas turbine engine includes: (a) a fan having at least two stages of rotating fan blades surrounded by a fan casing, the fan operable to produce a flow of pressurized air at a fan exit; (b) at least one heat exchanger having a first flowpath in fluid communication with the fan at a location upstream of the fan exit; and (c) a fluid system coupled to a second flowpath of the at least one heat exchanger. The first and second flowpaths are thermally coupled to each other.