I guess I should rule out HOU-IAH and IAH-EFD
since service is no longer operated with jets.
I did find an interesting flight, tho...DCA to IAD...somewhere around 20 miles. It's operated by Midwest Express... and flight time is SIX HOURS. It leaves DCA in the morning and then heads to the Midwest B/4 returning to IAD in the evening.
Unfortunately, Midwest Express does not publish a fare in the DCA-IAD market.
I wonder why?