The process of designing a Vapor Cycle System (VCS) for a fighter aircraft is a difficult and continuous challenge. Besides the constant efforts to optimize size, weight and package is the need to provide a highly reliable, producible and easily maintained system. In particular is the need to make the vapor compression system highly hermetic and intensely rugged.This paper updates the 1982 SAE paper entitled “Environmental Control of an Aircraft Pod Mounted Electronics System” (820869). Specifically it details the design, production and field results of the LANTIRN Environmental Control Unit (ECU). Since 1986 over 1000 of these systems have been fielded. The ECU has proven to be reliable in spite of the difficult environment, which has included combat duty.This paper will give insight into the LANTIRN pod thermal management system, the design of the ECU subsystem, and packaging. A major emphasis of the paper will be reviewing the design of the VCS with details on compressor design, operation of R114 and refrigerant inventory subtleties. The paper will also look at lessons learned on the LANTIRN program relative to the use of a VCS for the fighter aircraft environment and will peer into the future with respect to new working fluids and applications.The VCS has proven to be the right choice for the LANTIRN system. It operates directly from aircraft 400 Hz power and needs no engine bleed air. The use of electrical power instead of engine bleed air allows for a simplified interface between the ECU, pod, and aircraft. In addition the system is highly maintainable at the field level.