Flight

Robot-mode flight powers are a part of Transformer anatomy in the Generation 1 continuity family

Robot-mode flight powers are an innovative power that allows Transformers without a flight based alternate mode to fly while in robot mode. The Decepticons make good use of this power.

Sometimes the Autobots have them....sometimes they don't. Most often they display them early in Season 1 of the US cartoon, particularly the pilot. It is uncertain if they require external equipment to fly; several times the Autobots used strap-on jet packs or rocket packs, but sometimes they don't.

Robot-mode flight was prevalent in the post-movie episodes, in which the focus was shifted to space (perhaps, taking a hint from the Gundam franchise.) As although some characters could not fly under the influence of a planets gravity, 'everyone' seemed to posses the power of flight in deep space.

Ficiton

Generation 1 cartoon

Robot-mode flight powers were a technological innovation that allowed the Decepticons, who had just mastered the art of Transformation, to start a new war and battle the Autobots for supremacy of Cybertron. Their initial attacks were not a matter of public knowledge, and some Autobots, such as Orion Pax and Dion, admired them for their innovations. This admiration was ended when Megatron blasted Orion, Dion, and Ariel. It was to Megatron's detriment, however, for Alpha Trion rebuilt Orion and Ariel into Optimus Prime and Elita One. War Dawn

Eventually, the Autobots also mastered robot-mode flight powers, and they used them to reach an oil rig which the Decepticons were plundering. More Than Meets the Eye, Part 1 Ironhide and Bluestreak pursued the fleeing Decepticons into the air, though Skywarp had little difficulty shooting down Ironhide. Optimus required the use of Sideswipe's rocket pack to catch up to the space-bound Decepticon ship shortly afterwards, implying a limit on the speed or range of his flight capabilities. Sideswipe and Sunstreaker also used robot-mode flight powers in their use of jet judo against seekers attacking the Autobot base. Roll For It

The Autobots' ability to fly in robot mode effectively vanished after that. To reach Dinobot Island, Optimus Prime and a crew of Autobots used strap-on jetpacks. Even Autobots with flying alternate modes did not seem able to fly in robot mode, though Cosmos seemed able to maneuver in space while in robot mode.

The newly-created Dinobots could fly in robot mode, an abiliy they consistently demonstrated throughout their history.

In the years following the defeat of Unicron, a number of Autobots were seen to fly through space without any visible aid or means of propulsion. Notable among them was Perceptor, who had never before demonstrated such an ability. Before one such instance, Sky Lynx advised the Autobots in question to "don your rocket packs, gentlemen!" The Technobots all flew in robot mode from Earth to Saturn's moon Titan.

Despite the Autobots' rare display of this ability, some claim they do not have it at all. Galvatron once said outright that "Autobots cannot fly," himself flying easily over a booby trap, while his apparently earthbound Autobot companions remained helpless. The Return of Optimus Prime, Part 2

From Teletraan I: The Transformers Wiki, a Wikia wiki.