Often1

Many flights are overbooked (more seats sold than physically exist), but few are oversold (more properly ticketed passengers at the gate and prepared to board by the time required). People cancel, they misconnect, they get in traffic jams and so on.

It is not worth overthinking this and it is unlikely to work to your advantage to do so.

On the other side, as to upgrades, BA also tweaks its upgrade pricing to account for cabin overbooking. If WT is overbooked and at risk of oversale and there are seats in WTP, easier to sell an upgrade for little than to OPUP a passenger, that being the last resort.

Tilly71

How can you tell if your flight is overbooked in your cabin?

flatlander

Often1 is quite right. This means that if you think your flight is oversold and you'd like a cheap upgrade and you're willing to pay, look out for an offer when checking in and if none is offered then ask again at the airport for a paid upgrade (do make sure you say "paid", to avoid looking like a scrounger). If the price is acceptable, pull out your payment card and enjoy the experience onboard.

orbitmic

Which, of course, only works if you are o/d as there are no OLCI upgrade offers on connecting itineraries which many of us travel (and which is my case tomorrow), sometimes with too short a connection for an AUP to be a realistic option either.

In any case, fully agree that nobody should ever expect an upgrade, and also that whilst overbooking can be assessed, it is never possible to be sure of what will happen on the day. As Often1 mentions, you can easily have 20 people missing their connection and then your flight may leave with empty seats even if it was expected to leave with some passengers left on the ground. But then conversely, it just similarly takes 20 people to have missed their connection on the previous flight for your flight due to leave with some empty seats in all cabins to suddenly prove oversold.

That said, not all search for knowledge and information is utilitarian, and not all utilitarian information about loads relates to simplistic upgrade/downgrade potential. Whilst expecting information about cabin filling to tell you if you'll be upgraded or not would be highly naïve, there can be many other reasons why one might want to know the likely load of flight ranging from "pure" knowledge to decision on what seat to choose and more.

Swanhunter

From past experience, volunteering to help will be met with blank faces, especially if the station you are starting from (CPT) isn’t the affected one. I’d continue my journey as normal.

navylad

Whilst you can’t be certain from Expert Flyer, if gives you a good idea. In my case, with lots of zeros on the availability, I asked a friend in BA to check the actual status.

indeed, and whilst one needs to be realistic, it doesn’t harm to know your options in case you are offloaded- knowing there is an alternative connection that would mean getting to the airport 30 minutes earlier for it to be a possibility is prudent planning.

UKtravelbear

From what people like c-w-s have said in the past they are more likely to offload people on simple O/D trips than those with connections and especially international connections.