Oneway/RTStar AllianceAir Canada: No/1 stop + 1 stop OR 1 OJ
ANA: NA/4 Stop (max 1 per city) + 1 OJ
Asiana: ??/4 stopovers + 1 OJ
Miles & More (LH,LX,OS,+:) Yes/1 each way, not in origin region + 2 OJs
Singapore: Yes/??
Turkish Airlines: ??/??
United: No*/1 stop + 2 OJ
OneWorldAmerican Airlines: NA/No
US Airways: NA/1 stop OR 1 OJ
British Airways: Yes/Yes but doesn't matter on price, since they charge distance based **
LAN: ??/??
Qantas: Yes/Yes but doesn't matter on price, since they charge distance based **
Royal Jordanian: ??/??
Sky Team
Alitalia: ??/??
Air France/ KLM (Flying Blue) No/1 stop
Delta: No/1 stop + OJ
OtherElal: ??/??
Emirates: ??/??
Etihad: ??/??
JetAirways: ??/??
Virgin: ??/??
Alaskan: Yes/OJ or stop
p.s.NA: Program doesn't allow oneway bookings
No: Program allows oneways, but doesn't allow a stopover on a oneway
Yes: Stopovers allowed on oneway bookings
* It is technically not allowed, but with enough HUCA and persistance it can be accomplished. YMMV.
** any stopover option would need to be done over the phone.