From IMDB:

In the 1930s, three friends witness a murder, are framed for it, and uncover one of the most outrageous plots in American history.

On the plane back from London I watched this 2 hour 14 minute complete film.

Based on true facts, the film can still be called a comedy because it is full of almost outrageous antics by the three dedicated friends Burt, Valerie, and Harold.  In time you will figure out who the bad guys (i.e. traitors to the U.S.) are and how they related to the trio of friends.

To clinch the patriotism theme, Robert de Niro does a somewhat corny but effective job as General Gil Dillenbeck.

Look for several cameo appearances.

Good enough for a plane trip!