Flying DL code on WS - pricing / fare classes
 

This is more curiosity than anything else, as the price increase was not that much, but help to educate me please if you can and will.

I am looking at flying WS metal on a DL codeshare to YYZ. The DL codes tend to cost a little more than the WS codes, not uncommon for codeshare (I am seeing the same for UA codes on AC) and that's no big deal. But here's where my confusion arises:

The past several days, I've been watching flights, waiting for my dates and times to solidify so I can book. The price for the DL codeshare was $X. I did not note what fare code the DL flight number was booking under unfortunately. Now, the DL coded flights for the date I've locked in have all increased $25 more than the $X price ($25 is not the end of the world, thus why this is mostly curiosity). This new price is booking into T for the DL flight number. However, EF shows inventory open for X and V (which I think are lower fare classes?) for the DL flight number. In addition, and this likely means nothing, the WS coded fare has not changed.

Any idea if there is some sort of IT wackiness happening here; or if this intended, why EF is showing X and V DL inventory but DL is booking into T?

Thanks!

Do you meet the fare rules for any published fare that books into the relevant X or V inventory?

Absolutely no clue as I am a fare rule dummy. Yeah, I've been flying frequently for a decade now, but fare rules are never something I've ever really needed to dig into.

Not sure it matters, but this is a non-step, single segment flight I'm talking about.

If I am looking at the fare information results on EF correctly, there definitely are published valid fares under X and V, and I am outside of the advance purchase window for those fare. And the T fare listed on EF should be $X not the $X+25 price I'm seeing (which looks like a U fare per EF) so now i'm even more confused :)

Need to know route/date to be able to give more detailed reason.

Did you look at the flight application rules? I believe all the DL X/V fare filings for LGA-YYZ specifically require that you fly DL/Connection metal. There are specific T and higher fare filings that also allow for WS operated codeshare flights.

Here's the requirements on a V fare on LGA-YYZ. No WS allowed.

VA7SA0MQ
FLIGHT APPLICATION
THE FARE COMPONENT MUST BE ON ONE OR MORE OF THE FOLLOWING ANY DL FLIGHT OPERATED BY DL ANY DL FLIGHT OPERATED BY 9E ANY DL FLIGHT OPERATED BY CP ANY DL FLIGHT OPERATED BY EV ANY DL FLIGHT OPERATED BY OO ANY DL FLIGHT OPERATED BY YX ANY DL FLIGHT OPERATED BY G7.

And here's the applicable T fare that permits flying on WS. There are other cheaper T fare filings, but like above, they require DL/DL connection metal.

TA0LA0MS
FLIGHT APPLICATION
THE FARE COMPONENT MUST BE ON ONE OR MORE OF THE FOLLOWING ANY DL FLIGHT OPERATED BY WS IN COMBINATION WITH ONE OR MORE OF THE FOLLOWING ANY DL FLIGHT OPERATED BY DL ANY DL FLIGHT OPERATED BY 9E ANY DL FLIGHT OPERATED BY CP ANY DL FLIGHT OPERATED BY EV ANY DL FLIGHT OPERATED BY OO ANY DL FLIGHT OPERATED BY YX ANY DL FLIGHT OPERATED BY G7 ANY DL FLIGHT OPERATED BY WS. THE FARE COMPONENT MUST BE ON ONE OR MORE OF THE FOLLOWING ANY DL FLIGHT OPERATED BY WS.

Cheaper T fare, but note only DL/Connection metal.

TAVSC2MQ
FLIGHT APPLICATION
THE FARE COMPONENT MUST BE ON ONE OR MORE OF THE FOLLOWING ANY DL FLIGHT OPERATED BY DL ANY DL FLIGHT OPERATED BY 9E ANY DL FLIGHT OPERATED BY CP ANY DL FLIGHT OPERATED BY EV ANY DL FLIGHT OPERATED BY OO ANY DL FLIGHT OPERATED BY YX ANY DL FLIGHT OPERATED BY G7.

That kind of fare rule work isn't pleasant but is necessary to understand certain situations. LBJ helped you out. 99% of the people, 99.9% of the time, can just use a booking/search engine (Google Flights, Orbitz, etc.) to find eligible itineraries without getting into fare rules and adv purchase, min/max stay, routing, eligible carriers, max permitted miles and all that stuff.

As a general rule a fare class can be open but might not be bookable, for various reasons. For example some fare rules might require a 7-day advance purchase, but the fare bucket does not go to 0 at the 7 day mark -- you just stop being able to book tickets in that bucket. Or some fare classes may only be valid on roundtrips, so you will see a higher fare class if you go to book a one-way ticket. There are many other variations like this which can be important to consider when referring to EF data.

This can also be important for doing same-day changes with Delta, which require the same fare bucket to be available in order to confirm a change to a different flight. In some cases if you are booked on one of the cheaper fare buckets Delta.com may not let you book a new ticket in the same fare bucket due to advance purchase or other restrictions, so one might assume that same day change was not possible -- but EF can show that sometimes in fact the lower fare buckets do remain open despite not being newly bookable, in which case same day confirmed changes are possible.

Thanks all for the education, I appreciate it!

Related (but not fare related) question: outside of being able to access the SkyClub (using my Reserve card) and the 500 MQM, is there any other benefit to booking the DL flight number vs the WS flight number?