Dual Inventory Fares - Is there an idiot's guide anywhere?
 

Apologies if this has been posted before, is there and idiots guide to dual inventory fares and how they work anywhere?

Thanks

The best I found was a few threads discussing it, this is from the section in the TP thread on DIFs:

Thanks KARFA. I was wondering why I could see a shed load of cheap I class fares on EF but they’re all DIF, this probably explains it.

I don't recall seeing one specifically about DIFs.

The concept is really quite straightforward. Take a number of hypothetical flights on which the WT+ and WT availability looks like this (the reason for the bolding will be obvious later):-

1. W9 E9 T9 Y9 B9 H9 K9 M9 L9 V9 S9 N9 Q9 O9
2. W9 E9 T9 Y9 B9 H9 K9 M9 L9 V9 S8 N6 Q1 O0
3. W9 E9 T9 Y9 B9 H9 K9 M9 L6 V3 S0 N0 Q0 O0
4. W9 E9 T9 Y9 B9 H9 K9 M6 L3 V0 S0 N0 Q0 O0
5. W9 E9 T0 Y9 B9 H9 K9 M6 L3 V0 S0 N0 Q0 O0

The cheapest WT+ fares book into T class.

Consequently, a standard WT+ fare (ie one that is not a DIF) can be booked onto any of those flights except flight 5, for the straightforward reason that there is no T class on that flight.

However, BA may also file a number of T class DIFs. Each of them will require availability in T class, in the normal way. But in addition, there must be inventory in a specified WT class. So (hypothetically) there might be DIFs for this route that require availability in:-

1. [*]
2. [*]
3. [*]

As you go down that list, the fare will go up.

If you try to book on flight 1, the cheapest DIF (fare A) will be valid, because there is both T class availability and O class availability.

If you book on flight 2, fare A will not be valid because there is no O class on that flight. However, fare B will be valid because there is N class.

Similarly, on flight 3, neither fare A nor fare B will be valid, but you may be offered fare C because there is V class.

And on flight 4, the only DIF that is valid is fare D because L class is available but nothing lower.

It goes without saying that none of the DIFs is valid on flight 5 - not even fare D - because although there is L class in WT, there is no T class in WT+. Fare D, just like the standard non-DIF fare, requires there to be T class availability as well as availability in the specified WT+ class.

One of the frustrations with BA's current implementation of DIFs is that if you look at the EF fare ladder, it is impossible to tell which underlying WT booking class is required for that fare. You can sometimes work it out by trial and error by looking at different flights with different WT availability and matching the fares on the fare ladder to the fare quotes for each flight. But I have since decided that life is too short and gone for rather more empirical ways of checking that I'm getting the fare that I expect to get.

As found on google, I hope this document (geared towards the Malaysia trade) provides some insight...

This reminds me of "If airlines sold paint..."
http://www.travelweekly.com/Agent-Li...nes-sold-paint

DIF fares all appear something like TEUX35R/DIF4 in ExpertFlyer, eg here for LHR-MCT WT+ fares with dual inventory required in WT:
But if you are using ITA Matrix only the part before the / is shown when it tells you which fare covers each part of the journey. However I have yet to see a DIF fare with the prefix part before the / that was shared with another fare, so you can still work out which fare it is.

BA's website or callcenter or airport staff are the only places to buy these fares and there they simply show up as very cheap WT+ fares.

Expertflyer is bad at showing the fare rules for these fares, for example it will not show fare rules for most of the WT+ DIF fares, nor will it show the booking classes required.

If you do book one and happen upon Club award inventory...enjoy the long call to process the upgrade!

​​​​​​
i have upgraded DIFs using avios and GUFs and both were simple as normal :)

Thanks everyone for unravelling this. It’s very interesting.

I should have looked up the term but this is also the explanation for why my discounted transatlantic F/A is combined with a domestic Y/K. It seemed quite illogical when I was given that explanation by an agent as the web site explanation was that I was booked into the nearest equivalent class in the absence of F.

I rather suspect something different must have happened in your case.

In BA's implementation, I haven't seen different booking classes used simply because a DIF is valid and used to fare the ticket. If you book a standard (non-DIF) T class WT+ ticket on an itinerary like that, the short-hauls book into K and the long-hauls into T. If you buy a DIF, the same booking classes are used.

I've just tested this on an EDI-LHR-JFK-LHR-EDI using an A class DIF. That uses J class on the short-hauls and A class on the long-hauls, in the same way as if you book a non-DIF A class fare.

So if your short-hauls have booked into K class, I tend to think something else must have happened. I can't get ITA to combine any A class fare on the long-hauls with a K class fare on the short-hauls.

Dual inventory fare was the phrase used by an agent who checked with the fares desk and it seemed odd but I was not offered a further explanation. She did not seem to think that it was improbable. AA was offering the same flights as codeshares at the same fare but booking the UK domestic into J/I, however the CC discount trumped that option! Not that CE is worth anything but the extra TP would have been.

A Dual Inventory Fare is not the same as a fare that allows booking different segments of the itinerary into different booking classes. That is quite common and almost all long-haul fares allow it for short-haul connections. On BA, often visible as an I class business long haul fare booking into J class business for a connection on a short-haul flight. For example EDI-LHR-JFK-LHR-EDI. Also things like a business class short haul flight connecting to a first class long haul flight requires the use of a different, business class, selling code for the short haul flight.

When selling a ticket with a DIF fare, Dual Inventory is only required at sale time. So at the time you buy the ticket, there must be both availability in the cabin you will travel in the appropriate booking class (for example booking class T to get you into the WT+ cabin) and availability in some WT (economy) booking class, for example N. No N availability is taken away and unless you inspect the fare you will not know that N inventory was ever involved. The booking class remains T and you are booked into booking class T for all travel purposes.

If the availability on the flight was T3 and N1 you could book three such tickets.. But if the availability was T3 and N0 you could not book any of them. You would have to find some other, likely higher, fare.

Are you sure about the first part? I would have expected you to need N3 if you want to book 3 tickets.

I've done a quick test for LHR-JNB-LHR on 29 April outbound, 7 May inbound. (JNB is a good route on which to test this, because BA shows DIFs to ITA.) On the outbound, there is no difficulty with T class or O class availability, but inbound has T9 O1 and T9 O0 which could provide a test.

Pricing one seat with the availability checker switched off provides the lowest theoretical T class fare, which appears for all combinations (as one would expect): £1,314.61.

Pricing one seat with the availability checker switched on returns the lowest fare if using the earlier inbound flight: £1,314.61. If using the later inbound flight (on which the lowest economy seat is in L class), a non-DIF is used for that sector, and a much higher fare results (£1,448.61).

Pricing two seats using the earlier inbound flight returns a mixed result: ITA prices one seat at £1,314.61 and the second seat at £1,334.61. Both ITA prices use "TLXZ67S7" for the inbound half, and the gap between the prices for the two seats corresponds to the gap between one published TLXZ67S7F/DIF4 at £834.00 and the other published TLXZ67S7F/DIF4 at £874.00. The half round-trip fare components quoted by ITA match those published numbers when the £16.00 GDS fee is taken into account.

I can't be sure that the lowest DIF refers to O class but the results suggest that. And they strongly suggest that the last ITA quote for two seats is because you can only price one seat at the lowest DIF because there is only one O class seat. In other words, T9 O1 allows you to book only 1 seat at the lowest DIF, not two or three.

All the ITA quote numbers include the £16 GDS fee, so for simplicity I have not deducted that here.

Buying at the same time, you're right. I was thinking, but failed to write, "one after the other" or " three people could each buy a ticket" for same effect.

Ah yes, that could work - so long as buying T class seats doesn't cause the system to remove seats from O class (which in theory it could).

Are these xxxxxxxx/EUUP fares sold by AA also considered 'dual inventory fares'? And do they work the same way?
I tried to apply the same logic (availability in both classes) and never seem to be arrive at the right calculation.

Example: SLX8C1M4/EUUP for NCL to BWI
Which class codes require availability to get this one working?

Stan