Selecting Comfort+ after Travel Agent booking
 

I'm looking at flights and DL is pricing out a bit cheaper than UA is. This itinerary isn't bookable online (involves a second carrier that's not in the usual bunch), so I'll be getting a TA to book it. If they book as a straight economy purchase, is there anything stopping me from going online to my booking in order to select seats into Comfort+ (not premium select)? What's giving me hesitancy is on the DL website, it's showing as a separate cabin (even though it isn't).

Yes, Delta sells Comfort+ as a different fare and class of service than coach, it's not just another coach seat that you pay a fee to sit in. So, moving to Comfort+ will be a change in fare class. What I'm not sure about is with the TA booking is whether or not you will be able to upgrade online in the seat map. This is a new feature that allows you to select an upgraded seat and pay with money or miles, but I don't know how the TA booking will impact that.

A TA books most of my flights and it has no impact on upgrades or the ability to purchase C+ after the fact.

I can't speak to bulk/consolidator fares though.

You can always have the booking done by the TA and if you cannot book/upgrade into comfort+, you have 24 hrs to cancel and try something different.

All my corporate travel routes through a TA, specifically AMEX GBT (via Concur), and I've never had an issue with C+ (either with the option to buy when Silver or GM or upgrading from the list) or with upgrade as soon as the flight tickets (as PM)

In my experience in using CWT as my corporate travel agent, after I make the booking it takes approximately 25-45 minutes to ticket, then a few minutes on the delta side for the upgrade engine to process to upgrade to C+ (assuming seats are available). All told, about an hour after I book through the travel agent, it will show a comfort plus seat on the Delta app.

If OP could offer more details, OP would get a more informed response. Is OP a DL elite? Or, does OP intend to buy C+? What is the "other airline" involved? Generally speaking, it is possible to buy or upgrade to C+ on DL flights but there are edge cases where it isn't.

You should be able to go online and pay to upgrade to C+. If that does not work you could try calling. Delta might try to charge you a $50 fee in addition to whatever you pay to upgrade because they will be taking over a TA ticket.

Really, KC? Air Astana?

I believe you will need to have the Delta segment Delta-marketed, not something like 'AF xxxx operated by Delta'.

I've got a current ticket through Viking Cruises (likely bulk/consolidator rate that booked into V class) where it was pretty easy to buy C+ in either cash or miles on the transatlantic Delta-operated segments once the ticket went from reserved to conformed.

You’ve “never” had an issue?
Until fairly recently, it was not posssible on a TA-issued ticket to pay to upgrade booking classes without calling DL, and having them take over the ticket for $50. Maybe you don’t consider that “an issue”, but I do.
Now you can just select the seat from the seat map in any upgraded cabin, and DL.com will price the difference for you and you can confirm it, using $ or miles.

Never had an issue.

The times I've upfared, DL has never charged me the $50 to take over the ticket, just the cost difference between the corporate Y rate and the new fare.

The only time they've charged me is when I go through them to change flights during non-IRROPs situations instead of going through AMEX GBT (and I only do that in rare circumstances where I need to change something on the spot and don't have time to deal with AMEX getting in the middle).