Learn something everyday!! How does the "Juliet" come about though??
Since the UA-CO merger a lot of flights in the 800-900 have been getting alphanumeric ATC callsigns. The 800-900 range at UAL was used mostly for international flights and their connecting domestic legs. Prior to the merger dispatch would often be filing the domestic leg's flight plan with ATC while the international flight was still en-route (and active with ATC). For example, UAL916 would be routed LHR-IAD-SFO and the LHR-IAD leg would use UAL918, but the IAD-SFO leg would get filed as UAL8916. Since the merger it's more common that the LHR-IAD leg is filed as UAL916 and the IAD-SFO leg would be filed as UAL916T (or UAL916J, etc.)
Another example would be what happened last Saturday. UAL965 was scheduled from IAD to ORD. The inbound 67 was late into IAD and eventually they swapped it for a 57 already on the ground instead. Dispatch refiled with the ATC callsign UAL965T.