Different grades of Jet fuel
It's interesting that that two of the photo's above show North American operators. Here in Europe we use Jet A1 whereas in the USA it's Jet A. The main difference for airline operations is the respective freeze points (-47 C for A1 and -40 C for A) but a side effect is the visible smoke generated by so called "wide cut" fuels such as A. An even better example is the military equivalent used by US forces called JP5. Not only is this very smokey it is prohibited in civil use............