Does heavy air pollution improve takeoff performance? As you all probably know by now, aircraft have much better takeoff performance when and where the air is denser; this is why flights need to either use longer runways or jettison passengers and cargo on hot days (hot air is less dense than cold), and why a disproportionate number of the world’s longest runways are at high-altitude airports (air is much less dense at high altitudes than low).

Do aircraft see a similar performance boost at airports with heavily-polluted air, laden with dense gasses such as carbon dioxide, sulfur oxides, nitrogen dioxide, hydrogen chloride, nitric and sulfuric acids, and heavy hydrocarbons, plus lots of soot and tar particulates which raise the air’s mass much more than they do its volume?  Or is the benefit of having denser air swamped by the engine-performance penalty of having air with a lower oxygen concentration (a considerable quantity of said oxygen having gone into the formation of many of the aforementioned dense gasses)?
Percentages of pollutants will not have a significant effect on earth as compared with temperature and pressure.  However, on a planet like Mars, with a CO2 atmosphere, the density difference may be significant enough to effect lift calculations.

Maybe NASA could go with a twisted Prandtl biplane using a high altitude electric motor and prop.  They have reached 95,000 feet on earth with Helios, but had issues with structural strength.