Originally Posted by xliioper

On PHX-ATL, the cheapest roundtrip fares (XFVNH3MF) have Tue/Wed/Sat flight requirements (these are $418.20 roundtrip in Main). There's another roundtrip fare filing for slightly more (XFVNA5MF) that also allows Mon/Thu flights. There's yet another one (TFXNA0ME) that has no day of travel requirements. The AP requirements are pretty lengthy (21 days for the X fares and 45 days for the T fare). These are just the cheapest roundtrip fare filings (there are numerous other ones). The min stay requirements on these are fairly complex (it's not as simple as just a Saturday night stay and you can potentially book them for flights with a Satuday return without staying overnight on a Saturday). The min stay requirements found on delta.com (below) are only partial listings (the full section found on EF is actually much, much longer). The fifth position in fare basis code on domestic fares indicate day of travel requirements -- 3=Tue/Wed/Sat, 5= Mon/Tue/Wed/Thu/Sat, 0=no day of travel restrictions.