This paper presents particulate matter (PM) size spectral measurements, analysed to determine number and mass concentration, taken using a fast response differential mobility spectrometer (DMS500). Exhaust samples from multiple commercially available large civil aviation gas turbine engines and an auxiliary power unit operating at high and low engine power conditions were studied, in addition to a simulated aviation gas turbine exhaust, which was operated to exhibit specific PM output. Results show all exhaust sources as having similar bi-modal PM size spectra with both number and mass concentrations highly dependent on the emission source and the sampling testing condition. When operating at high power levels all of the tested gas turbine emission sources, with the exception of the 2-stage combustor design, generally produced distributions of PM which exhibited larger average mean diameter particle sizes and higher number and mass concentrations.