UA is apparently seeking to launch 3x weekly IAD-CPT flights to complement EWR-CPT. However, there are insufficient slots to accommodate both UA's proposed service and DL's recently announced/proposed 3x weekly ATL-CPT. UA has offered a compromise: that they divide the remaining 4x weekly slots into 2x weekly each. We'll see what happens.

Source: https://paxex.aero/united-airlines-dulles-cape-town/