My wife and I will be flying in June-July on the following award tickets: LAX-YVR-FRA-SIN-CGK [destination]-SIN-LHR [stopover]-YYC-LAX. The flights will be on AC, LH and SQ (made back when you could do this for 65k apiece in economy).

Yesterday I received a "Reservation Change Notification" showing that our SIN-LHR flight on SQ had been dropped. I checked on SQ's website and saw that the flight had not been cancelled, so I called United and they re-added that flight segment.

I asked the agent why this happened, and what surprised me was her answer. She seemed surprised and said, "It seems an agent cancelled the flight. To what end I do not know."

Any thoughts on why this happened? I did change the date of the LHR-YYC-LAX flights back on March 14 (without adding additional miles) but I just received the change notification yesterday (July 30).

No idea on how/why this happened, but do you mean "March 30" and not July 30?

It's not worth worrying about since it got fixed, but the distinct likelihood is that when this was originally booked, it was not properly or timely ticketed. Sooner of later SQ finds itself with a reservation but no payment (that's what a ticket, even an award ticket, is) and cancelled.

Anytime you make reservations, you should always confirm that you hold, not merely a reservation, but an e-ticket number for each segment of your itinerary. This particularly true when your ticketing and operating carriers are not the same and it is even more true on awards where there is the risk that your reservation on SQ is cancelled and there is no award space left and UA can't get it back.

Thanks for your replies. Yes, I meant March 30. And yes, I received my e-tickets right after I made the booking, which is exactly why this change was so surprising.

Receipt of a UA e-ticket confirm does not confirm partner ticketing. While it would seem reasonable to assume it does, it does not. That's why best practice is to confirm you're ticketed with the operating carrier.

And when you do contact the operating carrier don't be surprised that they were right and the flight was cancelled.

Just because it's still showing on their website doesn't mean that it has not been dropped. Give em a call and see what's up. Bypass UA on this one to obtain info on the straight poop!