...TOMASKEMPNER's post. PTY-EZE is 2879 nm, and I doubt that any North American 737 can beat that. ATL-JNB is the longest-ever nonstop (measured direct, at least). CUN-EZE is 3710 nm; CO's CLE-LGW 757 is 3269. MAD-EZE is 5432 nm, which is longer than MXP-SFO. And the MD11 does 6036 nm MXP-EZE (JFK-NRT is 5861, ATL-NRT is 5953).
So four "longest routes" end at Buenos Aires. Hm.