I think it is actually Amman.
OAG says winter schedule is:-
Code:
Day Flt No Via A/c
Mon BA6565 HBE 320
Wed BA6565 HBE 320
Fri BA6565 HBE 320
Sat BA6667 AMM 321
Sun BA6565 HBE 320
www.ba.com is a bit ambiguous but part of it ascribes the 321 to the Saturday flights too.