Given the data/analysis in this thread, I'm curious for everyone's thoughts on which types of routes it might be worth paying more for C+ for the marginally higher odds of getting upgraded? The obvious answer is long distance / low cost differential -- but I wonder if there are some types of flights for which paid C+ might more significantly increase the odds of getting upgraded than others.

Too many variables to actually say. When there’s only one available seat, it’s all but impossible to know why you’re #2 and identify if C+ purchase would have made a difference.

You will still get beaten by RUCs and 360s. And very frequently these days I am number 1 for 0 FC seats available.

Same Day Change is also a variable in "disappearing FC seats"

As a data point, all of my travel since late Dec 2023 to March 2024:
Diamond
1-2 MM
All travel Skymiles Award Travel
Upgrade success 13/15 legs, mix of routes / hubs / days of travel

Reviewing the upgrade list (after boarding) shows that other Diamonds who did not get FC upgrade are getting C+ seats as their upgrade (DIAMOND boarding zone). I infer that
1) award tickets are on same playing field as all-cash
2) the other Diamonds are lower number of Million Miles.

As far as C+ upgrades, C+ often full at time of booking (3/15 legs)
For C+ clearing at gate, on one recent flight (ATL-RDU) the other person ahead of me in priority was 1/60+ for FC (0/12 seats available) and 1/30+ for C+ (2/12 seats available)
I was 6/60+ for FC (0/12 FC available) and 2/30+ for C+ (2/12 C+ available).
I infer the Diamonds between us either didn't want a middle C+ seat, were traveling with another person and didn't want to split up, or already were in C+ before check in.

Is this a change to what "was before"? In other words, other posts have stated that MM status determination is based on lifetime miles. In reading: Medallion Upgrades | Delta Air Lines, there is this: Additional Things to Know About Upgrade Priority:

• Medallion Tier is the most important factor in upgrade clearance priority, starting with Diamond Medallion Members, then Platinum, then Gold and then Silver.
• Partner airline elite members will be eligible for day-of-departure upgrades only, with the exception of Aeromexico Club Premier members, whose upgrades can clear in advance or on the day-of-departure.
• All other things being equal, Members who have Million Miler Status will clear before Members that do not hold Million Miler Status. Members who hold the same Million Miler Status will be treated equally (regardless of progress within that tier).

In prior posts I have read about lifetime miles, which is in conflict with the above statement. Was there a change?
Seems pretty unfair how a person with 1,000,001, a 1MM, would be on the same "level" as a 1,999,999, 1MM . That is a substantial difference in miles flown. Of course there is the talk about BIS as compared to credit- card buying MM status, but that's for another talk, another time.

Any thoughts?

Good eye. It looks like the language changed sometime between June 9 and June 21:
https://web.archive.org/web/20240609...llion-upgrades

This was the old language:
"All other things being equal, Members who have Million Miler Status will clear before Members that do not hold Million Miler Status. For Members who hold Million Miler Status, the Member with the higher number of lifetime flight miles will clear first."

Pretty specific language in either case. So either they changed the process, or their documentation was incorrect and they updated it.

Did you check Wayback Archive? https://web.archive.org/web/20240609...llion-upgrades
Yes, it's a change. My guess is that implementation did not reflect wording (perhaps because getting actual MM balance is more challenging than simply MM status level) and they changed the wording to reflect the implementation.

A couple of data points on UG priority from recent flights
360 > DM (360 with no MM was ahead of me. Both booked in C)
C = C+ on domestic fights (I booked C, but DM with no MM who booked C+ was behind me)

For reference I'm DM/2MM

How did you know that the 360 wasn’t a MM? Wasn’t a 5MM 360? I never believed Delta that 360’s were not at the top of the UG list.

I would love to know the distribution of million milers (that is, how steep the curve drops off from 1MM to 2MM, 2MM to 3MM, and so on). It feels like 1MM bag tags are everywhere these days...I don't even use mine.

I've missed three UGs since February 1 as a newly minted lifetime DM with 3 MM status. The first miss was on a Monday afternoon in February ATL-CLE where I was #1 out of 61 for 0 F seats (I had never been #1 on a long UG list like this before). The second was where I was #2 for 0 F seats JFK-CLE in March. The third time was in April when I was #3 for 0 seats MSP-LAS (this was the flight where the FAs decided not to provide service to C+ and Y pax due to "turbulence" on a 3 hour flight, despite providing full service to the F cabin. I am 15 for 18 domestic UGs since February 1. Mrs. ND76 and I successfully used two of my 4 GUCs to get into D1 CDG-JFK and to F JFK-CLE ten days ago.

• All other things being equal, Members who have Million Miler Status will clear before Members that do not hold Million Miler Status. Members who hold the same Million Miler Status will be treated equally (regardless of progress within that tier).

I have a data point from yesterday that leads me to believe this change was botched in the coding process by Delta IT. I think, based upon my situation yesterday, all those with MM status are considered equal -- with the caveat that this was a situation where a RUC was in play.

I was on LAX-HNL yesterday. 2 seats in F left. My traveling companion is DM/2MM/Delta Reserve. I am DM/3MM/No Delta Reserve. Both of us had applied a Regional Upgrade. Both of us bought Main Cabin.

He was number 1 on the upgrade list. I was number 3. As a DM/3MM I should have been ranked above him (and always have been in the past when we are traveling together). Even more interesting, there was a person in between us at number 2.

I asked the gate agent how I would be ranked below a DM/2MM. She had no idea. She said, "I have been here 8 years and have not been trained on that." Basically, she robotically accepted the ranking as generated by the system and had no insight as to how it was assimilated, much less the authority to override. She was pleasant, and expressed the thought that she would like to know how it was derived, but she had no idea. She suggested I call the DM line. The flight was an hour late, so I had time an did.

I got a helpful agent on the line who did not dismiss my concern. She looked into it. She put me on hold and checked with others.

She came back with the answer that all three of us were DM on a Main Cabin fare applying a Regional Upgrade. She also affirmed that all were MM. She pointed out, however, that the other two had the Delta Reserve Amex and that I did not. In her research, including checking with a supervisor, she maintained that the number of Million Miles did not matter at all, that it went to the next tiebreaker, which is Delta Reserve Amex status.

So, either something has changed, or the system is malfunctioning. And, I think there is an outside chance that somehow Delta IT treats rankings when Regional Upgrades are involved differently than it does rankings when Complimentary Medallion Upgrades are involved.

Last week I was number 1 of 58 as only a MM DM with very high Reserve spend on a MC ticket and no RUC. I am consistently numbers 1-3 on very long upgrade lists so either 2/3/4MMs and 360s are not on my flights or Reserve counts for a lot and all MM are treated the same. Not complaining just a DP.

According to the Medallions Upgrade page:

• Enjoying Priority: Upgrade Certificates will clear off the waitlist in order of Medallion Tier then the day and time your request was added to the list. If you’re on the Airport Standby List, Upgrade Certificates receive higher priority than Medallion Complimentary Upgrade requests.

Million miler isn't a medallion tier. Therefore it would go by diamond and time of request.