Am I missing something? In the past I had looked for M-class tickets to get an upgrade using miles for TPAC flights, but they don't seem to be there any more. How does one buy an expensive economy ticket to get an upgrade on DL? Was this a NW artifact that I am remembering with fondness?

http://www.delta.com/booking/searchF...Type=roundtrip

At the bottom by Fare Class: pick M or Higher

But...

Before you buy the ticket, call (or use ExpertFlyer) to make sure they have Z inventory so you can actually use your miles to upgrade.

Buying a M or higher doesn't necessarily mean you will get the upgrade. I'm on a BOS-MSP flight currently, M Class, sitting in coach. Was #5 on the upgrade list. They wouldn't even let me upgrade using miles. If I didn't live in Atlanta, I'd certainly drop Delta. Luckily I'll be Gold in a few more flights. They certainly have flipped the finger to the Silvers recently.

I did that, but even up to the through "Review and Purchase" I don't see the option of upgrade. Do I do the upgrade after the purchase (knowing there are sufficient seats)? When I'm in the final "Passenger Information" page there is still no mention of upgrade. Do I go to "Continue" from there?

what he/she said, but

M is an expensive coach fare class, so it "should" be available on most flights, even close to departure and with minimum stay. However, I've noticed that the Shanghai flights seem full (early), especially the new nonstop DTW-PVG service. If you've only checked a few dates or if your destination is PVG (World Expo through October, IIRC), this could be the problem.

Also, sometimes B fares are not much more than M, IME a couple hundred dollars or about 10%. In the days of PMNW, this was handy because NW upgrades from full B came from a different bucket and cost fewer miles. You can combine one way in M with one way in B or Y too.

Finally, have you looked for a good discounted BE fare? IME this works better for Europe than Asia. On my last TPAC trip, M was just under $4K while the best discount BE RT I could find was over $7K about three months in advance of my departure.

In the past few months (but on NW), I had done the M class and before final purchase was asked if I wanted an upgrade for miles. Obviously I chose this, as that was the purpose of choosing M class. I thought I had seen this on the DL site, but now when I am about to get a ticket, it is not there.

Currently (SMI recently posted that this is scheduled to be enhanced around the end of the year) you must call DL for the upgrade. You cannot do it online and you cannot even check availability on delta.dumb. When you check the "request upgrade" box for a TPAC trip, it only shows EUA (if you're elite) upgrades as either available, request only or not available. For the TPAC or intra-Asia segments, the column is irrelevant for miles/SWU upgrades.

Follow the earlier advice and call before purchasing the M ticket. If you're elite, this is free. Otherwise, it might be possible to actually do the purchase online while on the telephone and have the agent do the upgrade instantly so as to avoid the $20 phone ticketing fee.

Also (this has been covered extensively in other threads), you need to check a week or so before your departure that the upgraded ticket has been properly reissued. Otherwise you will not be able to do OLCI (it's best to do this at T-24 to check for problems) and you will face a long and frustrating time at the airport, possibly ending up in a very expensive coach seat.

I know it's a pain, but get on the phone and make the reservation with an agent. Make sure to ask if you will be able to use miles to upgrade before you finalize the purchase. Even if you book online, you'll have to call put the upgrade through.

What everyone else said... You will have to call. FWIW, Delta still offers the 24-hour risk-free cancellation policy, so even if you booked first and then called, you could always cancel if the upgrade doesn't go through.

If you want me to check ExpertFlyer for you, just post (or PM) the dates and route.