The U.S. Air Force is seeking information from vendors with expertise in developing and producing a form-fit-function replacement for the APX-125 Advanced Identification Friend-or-Foe (AIFF) Combined Interrogator Transponder (CIT) on the USAF F-16 Blocks 30/32/40/42/50/52 C/D models. The vendor must meet specific requirements, including being a United States AIFF manufacturer with past experience, having development and production facilities in the United States, and meeting US DoD security protection requirements. The contractor must also have a solution that meets minimum requirements, including an AIFF Combined Interrogator Transponder (CIT) system with modes 1, 2, 3, 3a, C, S, and 5 capability. Key points to consider: • The contractor must have a solution that meets the minimum requirements, including an AIFF Combined Interrogator Transponder (CIT) system with modes 1, 2, 3, 3a, C, S, and 5 capability. • The contractor must meet US DoD security protection requirements. • The contractor must have a Quality Assurance Plan that complies with SAE AS9100 and AS9102. • The contractor must provide a proposed solution for software development environment that will allow U.S. Government software sustainment facility to develop and maintain the AIFF Operational Flight Program. • The contractor must provide a proposed delivery schedule for Test assets, Low-Rate Initial Production (LRIP), and Production hardware.