The three sampling campaigns presented in this report (APEX-1, -2, and -3) focused on collecting the data necessary to update and improve emission factors (indices) and source profiles for commercial aircraft-generated PM. The specific objectives of this program were to: Develop PM emission factors (indices) and chemical profiles for representative commercial aircraft engines (primary objective) and Determine the effect of fuel properties (e.g., sulfur and aromatic content) and engine operating conditions (e.g., cold vs. warm) on the PM emissions (secondary objective). Measurements conducted by NRMRL during APEX-1, -2 and -3 were conducted in the plume, mostly at 30 m behind the engine, and as such represent the total PM emissions present at that location. This testing was conducted using the Diesel Emissions Aerosol Laboratory (DEAL), and resulted in the first EPA-generated emission factors for commercial aircraft engines since the late 1970s. Samples extracted at other distances were analyzed by APEX collaborators. This program was originally designed to also provide critical PM emissions data for artificially diluted exhaust (measured 1 m behind the engine) as well as for the plume after natural atmospheric dilution and cooling. This comparison of methods was conducted during the first two tests of APEX-1 using the NRMRL Dilution Sampling System (DSS). However, because of the aggressive scope of the remainder of the project, limited availability of the DSS, and the disparate results produced between the two methods in APEX-1, this portion of the study was deferred for further investigation at a future date.