Originally Posted by
gr8pirate
TK doesn't offer premium economy any longer and I don't know anything about waitlisting, but:
- you can upgrade using miles ahead of time if the particular fare bucket these upgrades book into is available. I think it's "I", but may be wrong.
- you can upgrade using miles at check-in if seats are available
- TK sometimes sell upgrades at check in. I remember LAX-IST being somewhere around 900 USD
If you upgrade from economy to business with miles all you need is an available seat, unlike a business redemption which, at the lower rate, is bucket dependent. Given that you would normally have to pay taxes and fees anyway, this can work out well if the underlying economy fare was well priced.