Originally Posted by
Aliquot
Of course 45 minutes is possible. UA doesn't sell connections that people won't make most of the time. There is nothing particularly time consuming about a UA-UA DI connection in SFO.
I mean, there is, though. Depending upon the arrival gate, it may be a considerable walk to the international gates. Furthermore, for an international flight, UA reserves the right to deplane someone if they're not at the gate 30 minutes prior to departure. Even if the flight arrives exactly on time, if OP is near the back of the plane, it's easy to imagine it taking more than 15 minutes to deplane and walk across the airport. (UA normally allows some leeway to connecting passengers, but OP would have no recourse if the gate agent is in a hurry that day, perhaps because of a big standby list). Furthermore, although UA will sometimes hold flights for connecting passengers, it's extremely difficult to hold SFO-SIN because the crew risks timing out; and it can be challenging to get UA to rebook on anything except the next UA flight, 12 hours later… assuming there's space.
Originally Posted by
Aliquot
Of course the shorter the connection the higher the probability that a delay will blow it. There are more 30 minute delays than 2 hour delays. It just comes down to your personal calculation considering the consequences of missing the connection (need to be somewhere at a certain time, other options to get to your destination...) and the extra cost in total travel time and $/points for other options.
One can argue what, specifically, is the Sensible Connection Time for a D-I connection at SFO. However, I don't think there is any reasonable argument to be made for "45 minutes."
An hour, I might do it, but then I tend to be very aggressive in terms of connection times. OP seems to put a high priority on reducing risk, so I'd recommend at least 1h15m for that connection. Others might recommend more (one person already suggested 2h30m).