I am trying to book a United flight from LHR-DEL in economy but have not been able to find any flights for that sector. I am looking for a revenue ticket. Upon calling United was advised that they don't fly that sector directly themselves and utilize their partners instead. I had never heard of that before so wanted to get advise from the pros whether that was correct info provided or should I call them again? Also, can a United e-certificate be used to book tickets through United on a partner airline?