the4aces

If first class opens up later is it possible to book the seat and change to it later?

RoadWeary

Are you talking about using a upgrade or paid fare?

I think that would be whole new ticket to change from business or economy to first.

SLC-YYZ

Yes, sort of.

I have booked a business/first award ticket (on UA metal) when there was only economy available on some segments. I was able to call when I saw availability come free for the higher class and I called the 1K desk and they were able to move me into the higher cabin.

If it is booking an econ award and waiting for availability I am assuming it is a new ticket which would mean refunding the old award ... I have done this while 1k so it was relatively painless AND cost free since I didn't have a booking fee and taxes were refunded.

Good luck.

Syzygies

Yes, as a 1K with no change fees, one can be flexible in using awards.

There are some technical advantages to booking round trip (gaming the stopover rules to produce a "free one way" which is described elsewhere so I won't elaborate), but these don't interest me so I always book a pair of one way awards for flexibility. Then one can rebook each direction as opportunities emerge. Saver First and such awards tend to appear very close in.

Last summer I let an agent convince me that this approach was no longer necessary, that I should simply book round trip and let them do their work. This was a failure of imagination on our parts. Our return consisted of a short regional jet hop followed by a mainline transcon with new Saver First availability. Because the needed class wasn't listing on the regional hop (where I didn't want to change my wife's seat) we couldn't claim the seat in transcon first without adding miles. And one can't add miles to a round trip award that's already in progress. I was only able to fix this by pleading with agents that I had been incorrectly talked out of splitting the ticket by an agent I could identify. I don't recommend depending on such discussions going your way; simply book two one ways.

Montereybay

I have booked like this a couple of times in the past year. Book your award in Econ and then call Premier desk. Ask them to put you on the waitlist for upgrade with miles. You will automatically be placed in the higher cabin and have your miles deducted. I did this on IAH-LIM-IAH when no BF Saver was available. I was cleared a few days before departure automatically. I was surprised how well it worked out.