A good example would be the beginning of Beast Wars, the only ones who could fly were Terrorsaur and Waspinator in their beast modes and Optimus Primal in robot mode as special ability. Things are different in other continuities, in most of them flight is mainly resctricted for those whose alternate form can fly or have flight as special ability. The last theory is that Autobots prefer to not fly because it consumes lots of energy, explaining why the Decepticons are so obssesed to obtain it. Other theory was that the the makers of the cartoon realized that the Autobots wouldn't use their land vehicle forms if they could travel by flight. There are several theories for the Autobots suddenly not flying, the most extended one is that Decepticons had advantage in the air due to the Seekers and they decided to fight mainly on land where they had the advantage. The truth is that all Transformers of the original cartoon can fly, not only the Decepticons, it was clearly seen in the first chapters of the cartoon and then in the third season when Autobots can fly in space. Is there any reason why this has not, or cannot be done?

If we accept that Transformers can be manually upgraded, it seems as though upgrading to provide flight/levitation capability would be extremely beneficial. We know that some Transformers have changed factions, including from Decepticon to Autobot, so the technology isn't exactly kept completely secret or hidden. Flight/levitation would be useful to civilian Transformers, just as they would be useful to military ones. Since Autobots/Decepticons were originally one mixed group, it seems as though they should largely have the same feature sets and abilities. They either require jetpacks, or can only fly while in their Alt-Modes (as planes, rockets, spaceships, etc). By-and-large, Autobots do not share this ability. In many of the continuities, the Decepticons are capable of natural flight while in robot mode (or possibly more correctly levitation). In some, this was largely a civilian vs military split others were a bit more ambiguous. In all continuities, the Autobots and Decepticons were originally one race which split into two factions.

Transformers autobot and decepticon