Yes. You do not need to have a round-trip ticket, but it needs to be a round trip itinerary.
So if it's like this scenario:
Originally Posted by
leftysauce
Has anyone booked a round-trip travel on separate tickets, some of which are purchased entirely with flight credit, and has gotten reimbursed?
For example, AAA-BBB booked with UA FTC and an eligible Amex card; BBB-CCC booked completely with UA FTC; CCC-AAA booked with UA miles and charged taxes&fees to the same Amex card.
Would it be considered a eligible?