It is still possible to fly on board a DC9-21 here in the U.S.
In fact, you can jump out of this DC9 as well via the integral rear airstairs.....although use of a parachute when doing so is highly recommended.
https://www.airliners.net/photo/Perr...CdXkAXXiBkPjow
And I believe this particular airplane was operated by Allegiant Air before it was acquired by Perris Valley Skydiving in southern California.