NOVELTY - The metal air fuel cell comprises a housing (22, 26, 28), a first pair of flat cathodes contained in a parallel orientation within the housing, a first pair of flat anodes positioned between the first pair flat cathodes and extending parallel to the cathodes, and a second pair of flat cathodes positioned between the pair of flat anodes and extending parallel to the anodes. The housing has an air passage through which air pass to the first pair of flat cathodes. The air passage is sealed by a gas permeable membrane. The second pair of flat cathodes encloses the second air passage.    USE - The metal air fuel cell is useful as a power source for portable electronic devices.    ADVANTAGE - The metal air fuel cell is thin, flat, flexible and environmentally and ecologically clean throughout its life cycle, and can be economically manufactured with maximized power output and long life.    DETAILED DESCRIPTION - The metal air fuel cell comprises a housing (22, 26, 28), a first pair of flat cathodes contained in a parallel orientation within the housing, a first pair of flat anodes positioned between the first pair flat cathodes and extending parallel to the cathodes, and a second pair of flat cathodes positioned between the pair of flat anodes and extending parallel to the anodes. The housing has an air passage through which air pass to the first pair of flat cathodes. The air passage is sealed by a gas permeable membrane. The second pair of flat cathodes encloses the second air passage, which is coupled to the housing to permit air to pass to the second pair cathode plates. The first and second pairs of cathode plates are electrochemically coupled by an electrolyte to the first pair anode plates. The cathode and anode are electrochemically coupled by an electrolyte such that the cathode and anode are electrochemically reacted to consume oxygen gas at a volume rate of V when produces a desired electrical current of I. The gas permeable membrane has a gas permeability rate and a surface area through which oxygen gas pass through the gas permeable membrane to the cathode. The surface area and the gas permeability rate of the gas permeable membrane are selected to permit oxygen gas to pass through the membrane at a rate Vm equal to V at the desired current I. The gas permeable membrane is configured to restrict the passage of water vapor through the gas permeable membrane. The gas permeable membrane is hydrophobic. The electrolyte is carried in a gel matrix having micro-cells, and is contained in a porous cellulose layer. The first, second and third cathodes comprise a three layered cathode having a gas impermeable hydrophilic layer, a gas permeable hydrophobic layer containing a current collector mesh and a transition layer between the hydrophobic and hydrophilic layers. The transition layer is progressively hydrophilic from the hydrophobic layer towards the hydrophilic layer. The first pair of cathode plates is made from a first single elongated flat cathode, which is folded into first parallel portions. The first anode plates are made from a single elongated flat anode, which is folded into second parallel portions. The second pair of cathode plates is made from a second single elongated flat cathode, which is folded into third parallel portions. The first single elongated flat cathode is corrugated to form first parallel portions each having a parallel pair of flat cathode plates. The single elongated flat anode is corrugated to form second parallel portions each having a parallel pair of flat anode plates. The second elongated flat cathode is corrugated to form of third parallel portions each having a parallel pair of flat cathode plates separated by a second air passage. The first and second single elongated flat cathodes are aligned with each other and with the first single elongated flat anode such that the first, second and third parallel portions are aligned with each other. Each third parallel portion is nestled within a corresponding second parallel portion, which is present in turn nestled within a corresponding first parallel portion. The first air passages are formed between adjacent first parallel portions. The first air passages are coupled to the housing such that air pass to the parallel pairs of flat cathode plates formed in the first single elongated flat cathode. The housing is configured to couple to the second air passages such that air pass to the parallel pairs of flat cathode plates formed in the second single elongated flat cathode. The anode has a homogeneous crystal structure, and is made of an aluminum-indium alloy formed from aluminum having 99.95% purity and indium of 0.2-0.6 wt.%. The aluminum-indium alloy is first melted at 660 degrees C and then cooled into alloy plates in non-equilibrium, homogeneous crystal-forming conditions and then the alloy plates are cold rolled to form the anode.    DESCRIPTION OF DRAWING(S) - The diagram shows a perspective view of a metal air fuel cell.    Cathode (12)    Cathode tap (14)    Anode (16)    Anode tap (18)    Housing. (22, 26, 28)