Savvy travellers and frequent flyers keep an eye not just on the travel class of their ticket -- business, economy, and so on -- but on the booking class of their ticket.
Also known as a fare bucket, fare bracket, fare type or booking class, this is a single-letter code used to represent a specific sub-type of ticket sold.
While a particular flight might have 300 seats divided into just two or three travel classes, there can be a dozen or more booking classes. Each booking class might differ in refund options, frequent flyer mile earning rate, change fees, and so on.
Why is booking class important?
Your booking class will usually affect how many frequent flyer miles you'll earn and often whether you can apply for a point-based upgrade.
It can change where you are on the upgrade list in case the airline is looking to upgrade people, and -- on US airlines -- whether you get extra-legroom seats when flying economy.
So if you or your corporate travel agent book a lower-earning or upgrade-ineligible booking class, you'll lose out on miles and status credits.
Decoding the alphabet soup of booking class jargon
The booking class is the single letter that often appears under the "details" section when booking, and may sometimes appear on your confirmation emails, ticket small print or boarding pass too.
You'll sometimes hear people refer to economy as "Y", and business as "J" , which are both booking classes -- but as an example, Qantas' economy is also booked as N, O, Q, E, G, L, M, S, V, K, B, H and X classes.
Booking classes are different, though linked, to the publicly-visible fare type (Flexi, Saver, Flexible, and so on) and the actual class of travel (business, economy, etc.).
Discount booking classes, especially in economy, can mean earning points at markedly different rates.
More confusingly, booking classes vary between airlines -- and airlines often use the same letters to refer to different classes.
"S class on Qantas is a fairly low Discount Economy fare bucket, whereas on Virgin Australia it is a Premium Economy fare bucket" notes travel specialist Alex Prez of MTA Travel.
So what can you do about it? And which are the ones to avoid? We've a bit of specific advice for business travellers on Qantas and Virgin Australia.
Flying Qantas? Avoid classes O, N and Q
Prez suggests that frequent flyers avoid economy booking classes O, N and Q internationally, as he says those tickets classes aren't upgradeable with points. They also earn points and status credits at the lower "discount economy" rate.
The "full economy" higher-earning classes on Qantas domestic of Y, B, H, K, M, L or V are eligible for points upgrades.
Internationally, you can upgrade from Y, which is a full economy class, or S, which is discount economy. But even if you book the upgradeable classes, don't get your hopes up if you're not a high-tier Qantas Frequent Flyer.
"Because [Qantas points upgrades are] based on status level and not on order of request (although within status levels order does count also), someone with a lot of points and no or low status has got very little chance of securing an upgrade," Prez explains.
"What ends up happening is people end up bypassing an O Class special and booking a V Class fare at significantly more in the hope of getting their upgrade -- which without status they often don't get."
"So they've paid more than necessary for the same seat. (That's) great for Qantas but not so great for the passenger hoping to use some of their hard earned points."
Overall on Qantas, booking class types for its own flights are mostly based on the Flexi Saver/Fully Flexible differences you're presented with when booking and there's a clear table for international flights.
When on a Qantas partner airline like British Airways, booking class types and earn rates are buried in the terms and conditions, get a little bit more confusing, and vary between partner airlines.
Flying Virgin? Book "Flexi" fares to upgrade
On Virgin Australia, the upgrade situation isn't quite such an alphabet soup.
The good news: domestic, New Zealand and Pacific Islands flights are upgradeable with Velocity Frequent Flyer points from tickets sold as Flexi fares, so you don't need to look at the booking class at all.
The bad news: Velocity point upgrades on Los Angeles and Abu Dhabi flights that used to be V Australia still aren't available.
The complicated news: Virgin Australia booking class eligibility and earn rates for points and for status credits vary, and partner earn rates vary dramatically, which can be confusing to the newer frequent flyer.
Booking classes elsewhere
Obviously, there are other airline loyalty programs out there (in fact, we use a portfolio of frequent flyer programs to avoid losing out on miles and points). They'll all publish their eligible booking classes in the frequent flyer section of their websites or in their program's terms and conditions document.
About John Walton
Aviation journalist and travel columnist John took his first long-haul flight when he was eight weeks old and hasn't looked back since. Well, except when facing rearwards in business class.