canadiancow

This requires me to point out the difference between UA SDC and AC SDC.

UA SDC requires same fare class availability. If you're booked in I class, good luck doing a SDC. I've offered to pay the $75 in the past, to be told it's not possible, because there's no I space.

AC SDC requires "positive space". I'm still not entirely sure whether that's "in the cabin" or "on the flight" (meaning I think I've been able to move onto an oversold flight because J was not full), but it's a much easier policy to follow.

So I suspect that's one reason. SDC is not equivalent on all airlines. I actually recall an experience where I booked AA F LAX-SFO after explicitly looking up their SDC policies, only to find out their F policy was not described as it was implemented. It ended up requiring a supervisor override to get me the SDC, because my fare class was not available on the flight I wanted. And this was paid F booked 28 hours out.

On AC, that would not have been an issue. SDC would have been possible, and actually free (since all paid NA AC J fares include free SDC).

That being said, I've certainly made use of the free SDC for Gold on UA, and it is a nice feature. But the last time I used it, I was looking for SFO-SAN. The flight my friend was on was $150. The cheapest flight that day was $100. I booked the $100 and SDC'd to the $150, free of charge. UA lost $50.

Another AC FTer told me he regularly books the latest reasonable Rapidair flight, knowing he will clear standby onto whatever flight he wants, every single time. So if the 4pm is $500 and the 8pm is $200, he's paying $200 for the 4pm.

I trust this has answered your question.

I also trust that you understand I have not expressed an opinion in this post, and have only been pointing out facts.