A gas turbine engine heat exchange system, comprising: a first multi-width channel heat exchanger (MWCHX) (108, 118, 300) configured to transfer heat between a first air stream (114, 122, 208, 210, 322) and a heat transfer fluid, wherein the first MWCHX (108, 118, 300) comprises: a first plurality of air-passage mini-channels (320, 702) configured to allow passage of the first air stream (114, 122, 208, 210, 322) therethrough, wherein each air-passage channel (320, 702) of the plurality of air-passage mini-channels (320, 702) has an air-channel width and an air-channel length greater than the air-channel width; and a first plurality of heat transfer fluid channels configured to allow passage of the heat transfer fluid therethrough, wherein each heat transfer fluid channel of the plurality of heat transfer fluid channels has a heat transfer channel width and a heat transfer channel length greater than the heat transfer channel width, and wherein the heat transfer channel width is less than the air-channel width; and wherein the first MWCHX (108, 118, 300) further comprises a first plurality of sealing layers (326, 600), characterized in that the first plurality of sealing layers (326, 600) is diffusion bonded to the plurality of heat transfer fluid layers (324, 500) such that a single sealing layer (326, 600) of the first plurality of sealing layers (326, 600) is diffusion bonded to a single heat transfer fluid layer (324, 500) of the plurality of heat transfer fluid layers (324, 500) to create a first plurality of heat transfer and sealing layer sets, in that each heat transfer and sealing layer set of the first plurality of heat transfer and sealing layer sets comprises: an etched internal intake manifold, wherein the etched internal intake manifold is configured to distribute the heat transfer fluid to the first plurality of heat transfer fluid channels; and an etched internal outtake manifold, wherein the etched internal outtake manifold is configured to receive the heat transfer fluid from the first plurality of heat transfer fluid channels. a first plurality of air-passage mini-channels (320, 702) configured to allow passage of the first air stream (114, 122, 208, 210, 322) therethrough, wherein each air-passage channel (320, 702) of the plurality of air-passage mini-channels (320, 702) has an air-channel width and an air-channel length greater than the air-channel width; and a first plurality of heat transfer fluid channels configured to allow passage of the heat transfer fluid therethrough, wherein each heat transfer fluid channel of the plurality of heat transfer fluid channels has a heat transfer channel width and a heat transfer channel length greater than the heat transfer channel width, and wherein the heat transfer channel width is less than the air-channel width; and wherein the first MWCHX (108, 118, 300) further comprises a first plurality of sealing layers (326, 600), characterized in that the first plurality of sealing layers (326, 600) is diffusion bonded to the plurality of heat transfer fluid layers (324, 500) such that a single sealing layer (326, 600) of the first plurality of sealing layers (326, 600) is diffusion bonded to a single heat transfer fluid layer (324, 500) of the plurality of heat transfer fluid layers (324, 500) to create a first plurality of heat transfer and sealing layer sets, in that each heat transfer and sealing layer set of the first plurality of heat transfer and sealing layer sets comprises: an etched internal intake manifold, wherein the etched internal intake manifold is configured to distribute the heat transfer fluid to the first plurality of heat transfer fluid channels; and an etched internal outtake manifold, wherein the etched internal outtake manifold is configured to receive the heat transfer fluid from the first plurality of heat transfer fluid channels. an etched internal intake manifold, wherein the etched internal intake manifold is configured to distribute the heat transfer fluid to the first plurality of heat transfer fluid channels; and an etched internal outtake manifold, wherein the etched internal outtake manifold is configured to receive the heat transfer fluid from the first plurality of heat transfer fluid channels.