A mounting and alignment system for building panels. A mounting bracket comprises a lower component affixable to a building support and an upper component from which a panel can be hung. A bearing assembly between the upper and lower components transfers load from the upper component to the lower component and allows the horizontal position of the upper component and thereby the panel to be easily adjusted. Mullion guides on the sides and extending over the panel top interact with mullion guides on other panels and automatically adjust the horizontal position of a panel as the panel is lowed in place from a relatively large horizontal placement tolerance a smaller placement tolerance required for other interacting structures on adjacent sides of installed panel. After the panel is installed, mullion guides on the adjacent panel sides can be removed.