Big Floating Head

Megatron's Big Floating Head was the vessel Megatron inhabited during the second season of Beast Machines. It could change between being an immense aircraft and, well, a big floating head (bearing a resemblance to Megatron's own head).

As a result of his original body falling into the organic core of Cybertron, Megatron was split into two entities: The purely biological Noble/Savage and the purely mechanical "Big Floating Head". The Head was inert, as it possessed no Spark of its own.

Inside the Head itself, Megatron often manifest himself as a slightly smaller floating holographic head.

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