How prevalent are siddhis in buddhism?

Abilities (such as flying through the air, walking through solid obstructions, diving into the ground, walking on water, and so forth) are performed by changing one element, such as earth, into another element, such as air. How does one expect to achieve them? I have read some commentaries which claim they are mere illusions on the path to enlightenment and that the true sadhka shouldn't be distracted by them and should aim for higher realms. Moreover are these claims made in documentaries true?