N20SW was delivered on 06/02/71.
N21SW was delivered on 06/10/71.
N22SW was delivered on 06/15/71.
N23SW was delivered on 09/29/71.
Southwest had planned to use the 4th plane for it's rugular schedule and to also do some charter flights, but the courts nixed the charter flights and Southwest had to get rid of one of it's 4 aircraft. (This is when the 10 minute turn came into effect.)
I believe the one they got rid of was the first aircraft, N20SW, which went to Frontier on 6/23/72. After that it went to Continental in June 1986 and was broken up in February 2000.
N21SW went to Aloha in July of 1978 and was broken up in December 1991.
N22SW went to Aloha in June of 1980 and stayed until July of 1987? The last known operator was Casino Express. I don't know if that aircraft is still flying today.
In September 1974, after Southwest received N24SW, N23SW went to VASP where it was converted to cargo, I think and it was broken up in March 2000.
I think the oldest 727-200's still in Southwest's fleet is NSW60 which doesn't fly, but is used for parts. It was delivered in November 1979.
N62SW was delivered in March 1980 and I believe it is still flying with Southwest today, at least that's what someone posted in an earlier thread about two weeks ago.
I tried to get this info from several sources and there was conflicting info on some of the sites, so I've made my best guesses here.