The steps from rolling around on its wheels to actually flying are pretty significant; not the least of which is satisfying the relevant aeronautical agencies, which tend to be more than a bit skeptical of airworthiness, especially the restoration of a certified wreck.
If you're really curious about Patriot and air defense in general, watch 'Habitual Linecrosser' on YouTube. He is a bit zealous, but he's active Army, a Patriot Master Gunner, and a trainer with the system.