How many axes of stable rotation does a brick have?

Question

Dimentions of the brick are 12" x 6" x 3".

If rotating brick is thrown in air,
the axis of rotation will remain in the same orientation
with respect to both the brick and stationary observer,
if, for example, the brick rotates around it longest axis.

Answer 1

Check this interesting animation on what happens which such a block is spun in the air.

Answer 2

Two stable axes, the longest and the shortest. The middle axis is unstable.

Answer 3

the eigenvectors