During this experiment, we observed variety of aerosol layers during vertical and horizontal profiles, ranging from aged aerosols from two major Asian dust storms to ultrafine particles from recent nucleation events. Aerosol layers observed during the flights were found in thin stratified layers ranging from altitudes of 1000 meters to 7000 meters and thicknesses from 100 to 1000 meters. Aerosol size distributions indicated cloud processed aerosol in some of the layers, while other layers were clearly due to secondary particle formation with over 90 percent of the number concentration smaller than 30 nm diameter. The results presented here highlight a rapid transition in the physicochemical aerosol properties and their effect on CCN activation during a straight, level flight leg at 3000 meters above sea level. Accumulation mode aerosol with a median diameter near 150 micron characterized the beginning of the leg: total number concentration (NCN) at 630 cm-3 and CCN concentration (NCCN) at 335 cm-3 at 0.2% supersaturation. This aerosol was probably long-range transport from Asia based on back trajectories. The relatively high activation ratio (NCCN/NCN = 0.51) suggests a large soluble component which may be expected for cloud-processed aerosols. The accumulation mode quickly yielded to a bi-modal distribution with a large ultrafine component (NCN = 1100 cm-3; NCCN = 32 cm-3). An increase in the critical diameter (based on integrating the size distribution to obtain NCCN) from 134 nm (accumulation mode) to 190 nm (bi-modal) indicates a change in the chemical composition of the aerosols as well. During the final section of the leg, ultrafine aerosol (diameter < 20 nm) accounted for most of the aerosol population (NCN = 2000 cm-3), and as expected, the aerosol did not activate into CCN (NCCN = 2.4 cm-3) due to the small size.