Auxiliary fuel tank systems for aircraft and methods for their manufacture and use. In one embodiment, an aircraft can include a fuselage, at least one engine, and a fuel system configured to distribute fuel to at least one of the engine and an aerial refueling manifold. The aircraft can further include an auxiliary fuel tank system operably coupled to the fuel system. The auxiliary fuel tank system can include a master tank assembly and at least one slave tank assembly. The master tank assembly can be removably installed in the fuselage, and can include a master tank body configured to hold fuel. The master tank body can be configured to pass through a door in the fuselage without disassembly. The slave tank assembly can be removably installed in the fuselage at least proximate to the master tank assembly, and can include a slave tank body configured to hold fuel.