Originally Posted by
SFO 1K
Just so I'm clear in my thinking on doing this on arrival at SFO, if something goes wrong and delays the SIN flight and you've already changed you could misconnect and be in bigger hot water. It depends on your tolerance for risk.
Not really. If you board anywhere close to on time at SIN, a four-hour connection is really excessive. As others have noted, you'll be back airside within 30 minutes of arrival. And if you miss, they'll just rebook you on a later flight.
In any event, even if you want to wait until you're in the air (or arrival), the App is the best vehicle for a very simple SDC like this.