Did you see this thread? Aero train anemic pulling
The real cure, assuming the traction tires are intact, is adding weight. I added about a pound and a half, it had a very positive effect on the pulling power and stability of the locomotive. My upgraded locomotive now pulls all ten of my cars.
Note that you should generously lub the Aerotrain cars, they have considerable rolling resistance when compared to most other passenger cars. Odd for such a small car, but that's life. I have given thought to removing the rollers from most of them and using a one-wire tether to lower the rolling resistance.
