Basic Economy Hack (international)
 

I found a good fare from JFK to Europe $600 (basic economy) on Delta metal... that same ticket is bookable on AirFrance (about $12 more, obviously wayyyy less than the approximately $150 "main cabin" upgrade on delta). If I book through Air France I can select seats right away - and DM Line stated I would be eligible for C+ at checkin.

Is there a downside I'm missing?

Where is sucks is on domestic connections. Just like C+ you wont be eligible for F upgrades till DoD. If no connecting flights there's no difference.

I am trying to add a domestic connection to pad my mileage total and there is another option for the same price through DTW. Air France's website lets me select a seat for the DTW to EUROPE segment, but not for JFK to DTW - are you saying I'll still be eligible for C+ or F upgrade on JFK to DTW on DOD - or is it some mutant itinerary where I can pick a seat longhaul, but not on the shorthaul? Depending on your answer I may just fly direct and skip Detroit lol

AF will refer you to DL for non TATL DL flights. C+/F will be available only on DoD for any segment not booked with DL code.

Am I misunderstanding this or are you?

My take is the OP is contemplating booking a cheap eco light ticket on AF/KL stock. DL operated flights will book into main cabin. His alternative is to book BE on DL.

There won't be C+ or F upgrades at all when he goes the second route. That is, it is better to have the chance of selecting seats at the time of booking and a shot at C+/F upgrade on the day of departure rather than not having those chances at all.

I thing you're actually getting what I'm saying, but dont realize it. I'm pointing out the only real drawback is that the flights will be coded as AF codeshare. Thus the main issue is that C+/F upgrades on DL metal will only be DoD. Thus the main drawback is that on domestic flights wont upgrade at the window. As long as OP doesn't care about that there's no drawback.

But if the OP is comparing this to booking BE on Delta, it isn't a drawback at all. It's an improvement, because BE is not eligible for an upgrade, ever. Unless something has changed with BE upgrades?

OP was also comparing to booking with DL and paying the extra cost to book regular economy. At least that's the way I read it.

I’ve done this many times and even gotten F on some domestic connections. But, it is also sometimes possible to get a AF/KL coded, DL operated long haul flight followed/preceded by a DL coded and operated domestic connection. Even if the underlying AF/KL fare is a basic or ‘light fare,’ the DL domestic connection sometimes (not always) books into a non-basic economy fare class (ie. V) and is therefore eligible for C+ and F at normal windows. Just gotta be patient and play around the ITA matrix website and book through an OTA.

I think you're misunderstanding things.

1)if flight (not ticket stock, but flight number) is sold as AF/KL marketed is what matters for upgrades. If they sell it using the DL code, normal windows apply. If using AF/KL code than DoD only.
2)Of course AF/KL can sell fares that include F on domestic connections. Has nothing to do with upgrades.
3)Unless something has changed, BE fares/restrictions don't happen with mixed airline bookings.

I think we're talking past one another. Yes, if all flights are AF/KL marketed, then obviously DoD is the only shot at C+/F on the DL operated segments. However, you can get an underlying basic/'light' AF/KL fare that books into non-BE on DL-marketed segments.

For example, I have an upcoming flight (actually, on 006 stock) that uses AF/KL fares with a B designator (second to last place in the fare basis) indicating it's a basic/light/hand baggage only fare. BUT, here are the flights:

KL1822 TXL-AMS L
AF3667 AMS-ATL V (operated by DL)
DL806 ATL-PHL V (as a PM, I've already cleared into C+)

another example is

DL1992 LGA-ATL L (C+ upgrade to SU)
DL3665 ATL-AMS N (operated by DL)
KL xxxx AMS-FCO N

My point was that you can book flights such that DL domestic connections don't book into E, even if its a 'light/basic' fare. In my experience, this has only worked where the transatlantic segments are AF/KL marketed. It takes some playing to get these to price out.

I hope this clarifies things and isn't too hard to follow! It still means you have to deal with no C+ upgrade on the long-haul segment, but softens the blow a bit (and saves at least $100 in most cases).

AF and KL super deep discount buckets now book or "map" into DL Basic Economy. You will not get main cabin benefits. Even if your fare bucket isn't "E" if you try and get any main-cabin benefits by calling DL and asking, they'll just tell you you're in basic economy.

I just booked this morning JFK to DTW to Europe and back for $600 and it let me pick my seats on all four segments. This is Air France Operated by Delta. So definitely worked for me. And yesterday I had booked the same ticket but just JFK to Europe and back for $600 and it let me pick my seats on both segments. So it definitely worked for me. :)

Not sure if this is true - I've never had an issue getting PM benefits (seats, upgrades) on these types of tickets when a flight is DL coded and non-E fare class. I do think trying to make changes would not be allowed.

I had heard if you book KL op and KL coded basic fare (or light) you can select seats (including comfort) if you are Skyteam Elite Plus (which a DL Diamond and Plat would be. Is this true? If so, is there any downside from booking light on KL?