I have the whole family including myself (1K) booked on UA 838 from NRT to SFO on July 13. I applied four SWUs and on the waitlist. 1K desk told me the upgrade will be all or none.

I searched KVS, UA 838 (747) shows C9 D8 Z8 J9, but XC0 and NC0, does it mean there is no more business upgrade. I searched UA website, there are 8 biz seat opens.

There is another UA flight 852 (777) on the same day but one hour later. KVS shows C9 D9 Z9 J9 and XC9 and NC9. UA website shows a ton of biz seat left.

My guess is that UA838 has lie flat bed so it is more popular. Does NC0 mean I have close to zero chance to get upgrade?

It appears that my chance is better on UA 852. Shall I call to change now or wait until the day to do same day change to avoid the fee?

Any advice will be greatly appreciated.