Considered and widely rejected due to issues like acid rain, ozone depletion, and decreased photosynthesis. Maybe if carefully distributed at optimal locations

Considered and widely rejected due to issues like acid rain, ozone depletion, and decreased photosynthesis. Maybe if carefully distributed at optimal locations and altitudes you could maximize the cooling effects while minimizing damage, but random emission from flights in no way optimized for that purpose? No, it's just pollution.