The defense argued that Hinckley's frequent flying around the United States was evidence of his insanity. 
The prosecution, on the other hand, argued that Hinckley's ability to plan and execute his travels was evidence that he was sane.

Two Weeks in October, 1980: The Travels of John Hinckley, Jr.

October 5: In New Haven
October 6: Fly to Lincoln
October 7: Fly to Nashville
October 9: Fly to New Haven
October 11: Fly to Dallas
October 15: Fly to New Haven
October 17: Fly to Washington, D. C.
October 19: Fly to Denver
Closing Argument Excerpts:

Closing Argument of Mr. Adelman for the Prosecution:
You know, look at those charts (pointing to chart showing Hinckley's travels).  [They show] Mr. Hinckley flying all over the United States.  This man is not a drifter or a loner stumbling around some little town in Nebraska running into fence posts.  He is flying United Airlines, he is flying American....Did you ever hear any evidence that Mr. Hinckley didn't have the ability to make the airline connections, to travel around and do what he wanted?

Closing Argument of Mr. Fuller for the Defense:
[You] can track very closely the defendant's travel through the months of the early fall and winter of 1981.  And I think these are all consistent with what I am suggesting to you now, that the defendant's motivating, driving forces are unreal, that [there has been] detachment from reality as you and I know it to be.