As always, I find the details of transportation to be important in shaping each Amazing Race leg. Leg 11 started with a trip to Edinburgh Central rail station for a 1 hour 10 minute average trip (there are 4 each hour) to Glasgow Central. That would put Max/Katie into Glasgow by just after 530pm, Bates/Anthony the same, Caroline/Jennifer there by 645pm and Mona/Beth there by 845pm.
The train schedule from Glasgow to Stanraer was fiendishly difficult to obtain (try it and see what I mean). At that range of evening departures, the trains would be:
dep. Glasgow Central 1830 arr. Stanraer 2059
dep. Glasgow Central 2030 arr. Stanraer 2353
The walk to the Cairnryan ferry terminal is reported to be 3 minutes or 6 minutes from either Stanraer station, but in any event the teams took taxis.
At the ferry terminal they bunched and I believe World Race Productions made a strategic decision to not allow them to take the 4am ferry to Belfast for filming reasons. They were on the 0730 ferry for unknown reasons, arriving 0945. Leg 11 finished with a pit stop and teams were released in Belfast the next morning. They were sent to the Stena line ship Belfast to Liverpool, which had this schedule:
dep. 1030 arr. 1830 after an 8 hour trip
The next train options to London-Euston from Liverpool-Lime St. were:
dep. 1848 arr. 2102
dep. 1948 arr. 2209
After the trip to the pub to find out their destination, teams could reasonably expect to reach Heathrow around midnight. The only reasonable choice would be United 923 LHR IAD 0723 1042 and the video showed a United plane taxiing into the gate at Washington-Dulles.