My family and I are trying to figure out what airline we want to take on our next trip (Thailand).

Our ideal situation is we would buy coach tickets and then use our miles to upgrade to business.

We have both Delta and Continental miles.

I am on the Delta website to see what our best bet is, and it says for all of their flights to Bangkok are "Delta flight XXXX, operated by Korean Airlines".

Can you use Delta miles to upgrade even if the flight is operated by another airline? (I am pretty sure I tried to use miles to upgrade on Air France once and couldn't, but I am not sure.)

Thanks!

You can't use DL miles to upgrade flights operated by Korean, sorry.

Looks like you can use DL miles to upgrade on SQ.

I <b>think</b> you can theoretically use CO miles to upgrade on NW. But availability is very limited.

I believe it has to be a full Y fare in order to use DL miles to upgrade SQ flights.

It looks like there are some Delta flights where Delta actually operates the flight, not Korean. (If the Delta website is not leading me astray!) So that would be an option.

Or maybe we will use miles to fly to Paris, spend a few days there, and just pay to fly Air France business class to Bangkok.

DL has started flying ATL-ICN (Seoul Inchon). But ICN-BKK (a 5-hour flight) will on be KE.

On DL operated flights you have to purchase a Y, B or M fare to upgrade with miles. Make sure there's upgrade availability before you buy a higher fare ticket.