In the previous decade two new concepts in modal analysis have matured that might benefit the processing of flight flutter test data: Operational Modal Analysis with eXogenous inputs (OMAX), and the concept of transmissibility functions. OMAX is a framework that involves the combined use of experimental data (apply force, measure response, estimate frequency response function FRF) and operational data (only ambient force e.g. turbulence, measure response, estimate power spectral density function PSD). A transmissibility function is the ratio between two measured responses: it thus represents the same information as is present in a PSD, but with the advantage that it is almost noise-free. Transmissibility functions were first introduced in operational modal analysis but have been extended to fit in the OMAX framework. In this paper we show how transmissibility functions can be used in flight flutter testing, both in OMA and OMAX context. This is done using a simulated flight flutter test based on real-life ground vibration test data.