Flyer Tip #5 - booking class availability myths

This is part of a series of blog posts on tips for flyers.

Why might this post be useful to you?

Previous posts in this series explained what are booking classes, and how you can use tools to look up their availability. This post helps you to interpret booking class availability by explaining away some myths and fallacies.

Fallacy - add up available numbers

An easy mistake to make is to add up the availability in a class of travel based on the availability of individual booking classes.

For example a flight may show the availability in business class as J4 D3 I0 - this does not mean 7 business class seats are available. It means the airline is willing to sell 4 seats (at least) in full fare business class, 3 in discounted business class and none in sale fare business class. I say at least 4 seats in full fare because this particular airline only shows a maximum of 4 in availability tools for first and business class. However, in this case it is probably 4 or 5, rather than a higher number, because the airline is not willing to sell many discounted fares.

Myth - from the availability numbers I can tell how full the cabin is

While low availability does suggest a full cabin this is not always so, for several reasons.

An example is a flight with 12 seats in business class. If availability shows J2 D0 I0 then it is intuitive to think 2 seats are available for sell means 10 seats have been taken - the cabin is fairly full.

The first reason this might not be right is that it ignores oversell situations. Airlines sometimes sell more seats than are physically available because they know a percentage of passengers fail to take the flight (called no show). If say more than 5% of passengers are expected to no show for a given flight, then they can make more money by selling say 2% extra seats. The extra revenue from the 2% more than offsets any costs if there are fewer no shows than expected. The no show rate varies a lot by route, class of travel, day of week, time of day, number of full fare/flexible tickets sold. Airlines monitor no show rates quite carefully and have models to predict the numbers.

The second reason is the schedule may give the airline flexibility to oversell, or to undersell, a flight. If a flight has a light load and there is another flight by the same airline a little earlier or later they might combine them. If the airline is planning for this event they may undersell close to departure to allow the 2 flights to be merged. Qantas is well known for doing this on their golden triangle route between Sydney, Melbourne and Brisbane. Similarly if there are two (or more) flights with varying loads they may oversell more aggressively one flight knowing they can switch some passengers to the other flight. British Airways and Qantas sometimes do this on the Kangaroo route between London and Sydney.

A third reason is allowing for the ability to move some passengers into a different cabin (usually higher cabin in an op-up or operational upgrade because a downgrade needs to be compensated for). If the first class cabin is fairly empty then an airline may allow business class to be oversold, similarly for empty business class and full economy class. Interpreting availability for business class and premium economy can be particularly tricky as you need to look at the cabin above and the cabin below since there may be cascading op-ups. This is where some passengers are moved from business to first to make room for other passengers being moved from economy to business, on a flight where economy is oversold and business class moderately full but first class is fairly empty. A number of airlines are taking this approach more this year than previously as it is proving to be much easier to get high loads in economy than maintaining them in first or business class.

See also below about the effect of codeshares on availability.

Fallacy - once availability is gone from cheaper booking classes it does not return

Availability isn't static or constant. It changes over time.

Availability reduces as people buy tickets. Someone buying a cheap fare reduces availability in that booking class. Someone buying a more expensive fare may reduce availability in all booking classes.

Availability may increase when people change their tickets, or the airline may decide not to release the seat back. This can produce odd results such as recent posts on Flyer Talk discussing saver awards on Singapore Airlines being available when standard (more expensive and thus higher booking class) ones were not available. In that case a cancelled award seat was re-released in the same booking class because it was close to departure and the flight was not full. However if the flight was full Singapore Airlines may have chosen to not add back an award seat and instead sell an expensive paid fare.

Airlines also review loads and bookings and tweak availability. Sometimes the airline's predicted patterns of sales do not eventuate and they may need to add more cheap availability or take it out if things are going better (from the airline's point of view) than expected.

Myth - a codeshare will show much the same availability as operating airline

It is easy to assume that availability of a given flight will be roughly the same for the operating airline as for the codeshare airline. After all, why would someone pay an expensive fare when they could get it more cheaply with a different airline on the same flight?

The reality is there is the relationship between availability of operating airline and availability of codeshare partner(s) depends a lot on the nature of the codeshare and several other circumstances.

Some codeshares are of the form of profit shares and work much how you'd expect in that availability is close or even identical. Examples of this include Lufthansa and United on their trans-atlantic flights and Qantas and British Airways on the kangaroo route. Note if the codeshare airline booking classes do not mean exactly the same thing as the booking classes of the operating airline (eg booking class E on one airline is the same as V on the other), availability tools may show an apparent difference that is not real.

Some codeshares are commitments to sell a certain number of seats on a flight. In these cases availability can differ widely between operating airline and marketing (ie codeshare) airline. Sometimes the operating airline will be cheaper (or have availability) and sometimes the marketing airline will be. A recent example was a friend looking for an AAdvantage frequent flyer award between Sydney and Auckland on Christmas Eve - the LAN flight had no availability under the Qantas code but did have availability under the LAN code. It is normally the other way around on this particular flight but because it is Christmas Eve all the Qantas award seats have long been snapped up. LAN does have many frequent flyers based in Australia or New Zealand and thus still had award seats available.

The codeshare airline may or may not have the ability to release unused seats to the operating airline, or get extra seats. Any inventory changes between the airlines may be at certain times (eg one month before departure) or it may be at any time. It depends on the (unpublished) details of their agreement.

Where there isn't an adjustment clause the difference in availability can be enormous. I've been on flights between New Zealand and Japan (operated by Air New Zealand with codeshare by Japan Airlines) where almost every passenger onboard was on a ticket by the codeshare partner.

I've also been on flights were it is impossible to buy a seat from the operating airline for some weeks before departure until the inventory adjustment was made a week out and suddenly cheapish fares are available. In those cases the codeshare airline had not sold many seats and the operating airline went from having no seats for sale to a lot available to sell close to departure.

A more technical issue that is relevant in some circumstances is where the operating airline and codeshare airline use different CRS (see this post on CRS for an explanation and summary of which airline uses which CRS). In this case the availability showing may not be quite in sync making it possible to nab a seat when the flight is full.


This post is long enough I think, and so I'll save some more flyer tips for another post. Happy travels.