Originally Posted by
nebratu
If i book it as a multi-city trip option on UA's website, but depart BWI or IAD and return to DCA, would it be considered a r/t?
Normally you have to start and return to the same airport to be an RT.
Read the rules or terms and conditions of the ticket you are purchasing or the program you are trying to meet the qualifications for. They will be on the UA web site.
Also note that if you are flying to the West Coast, most non-stop return flights only use IAD or BWI. That may be why you can't find a return flight to DCA.