Oh well, back to the drawing board. Thanks to all for their opinions.... was very pleasantly surprised by the responses on here

Maybe it is all children on this post, but those who might remember the late 70s would recall theperfectly legal transatlantic standby tickets. It was a reaction by the legacy carriers (at the time BA, TWA and Pan Am) to thwart the startup Laker Skytrain. You paid your money and then stood in an overnight queue outside the London town terminal and when these places opened around 0700 you either got confirmed or rejected.
A further development was the famous TWA 'Budget' flight, where you simple choose the outbound and return week, and then the airline allocated you a place on the emptiest flight, a week before hand. Then it was 'use it or lose it'. This one was a nightmare because you could end up going out begining of one week and back at the end of the next, or alternatively it could be out Saturday, back Sunday. The passenger had no control.
I worked in one of these airline's res. office at the time and spent many an hour arguing with passengers who were not happy with their allocated flight. Tough!

Not quite children, because not only do I recall those standby tickets, or actually refer to their commercial downsides in my post just above, but I actually used them on multiple occasions on BA to Los Angeles in 1978-80. It had just changed over from the leased Air New Zealand DC-10 to the new BA 747-200B, plus a daily BA flight had been started at the same time to San Francisco, so there was plenty of capacity to California.

About £200 return. Not only that from London, but from any other BA domestic station as well by connection, so I once got an inclusive sector on the One-Eleven down from Manchester, buying the ticket at the BA counter at Ringway. On another occasion I walked mid-morning into the old BA overseas ground terminal at Victoria, there was a nice display board with the status of all standby destinations that day; all had space except Washington, marked "flight full".

Overnight queues were a feature of the Laker operation, and only on key dates anyway, such as all the US college students returning at the end of the summer.

I then joined a major worldwide corporate, whose UK office was near Heathrow. Headquarters in Detroit, and the MD was from there; there was of course a lot of travel to and fro. The MD had a Daimler plus chauffeur provided, old Reg who had the job for years and had seen many an MD come and go. One day we all got yet another memo about cost-cutting; this one was saying that travel costs to Detroit were to be reduced by using standby from now on, as in "his experience" there's always room. He was an accounting cheapskate, even he went economy. This was of course a significant nuisance as you now had to go to a BA office at 8 am to get the ticket for the afternoon flight.

We had a branch office in Newcastle, and the manager there came down to the London office one day on the first BA domestic. Walking out of Terminal 1, who does he see standing in the ticket counter queue but Reg the chauffeur. "Hello Reg, what are you doing here ?". "Oh, Mr X is going to Detroit this afternoon, so I've just come down for his standby ticket. Hang on a few minutes and I'll give you a lift back to the office ...".

I don't recall those TWA tickets at all, at least not from London.

I've previously bought such a ticket in Sweden. I think it was Next Air that had cheap standby for 25 or younger. You just turned up at the airport and bought a ticket if there was free seats

There used to be Standby tickets in Australia during the 1980s (and probably earlier). I used them a few times. Airlines soon figured out that if you wanted to travel on a particular day, you'll pay... So standby tickets became the preserve of ID90 etc.

Yield management is a bit of a "dark art". I remember getting on a flight ex-Rio that was -57 on an ID90. No issue getting on. Some routes were notorious for no-shows, usually in F and J. If you made LHR-JFK a standby route, I wouldn't fancy my chances if it was overbooked.

It's not a dark art at all to those experienced in it. LHR-JFK on BA would be quite a good chance, because one of the more common reasons (of many) is late arrival of an inbound connecting aircraft (or stuck in transit security etc); on a US carrier less so because they have less connecting passengers at the London end, more at the US end.

And it depends when you look. In the morning you may well be grossly over like this. As people rebook onto earlier flights, or tomorrow, or whatever, the numbers change through the hours. Being 50 over on a widebody is nothing unusual on certain routes.

yes - I can remember being waitlisted at #156 on a KLM 737 AMS-LHR at one time.........................

It used to be that buying last minute was cheap - now it's expensive. Life has changed immeasurably in the last 50 years and the speed of life and the business cycle has mean that people prize being able to change and move quickly. Sometimes you can get a low cost last minute but all carriers found that holiday traffic in particular was not booking early and waiting till close to date and then picking whatever was cheapest. So we don't have much of that any more!

They want your money earning them interest for as long as possible.

There is absolutely nothing from a regulatory perspective to prevent an airline from offering standby seats if it wished. The question has to be "why would you?".

On EU261, the regulation only applies if you have a seat confirmed (Article 3(2)(a)). Up to the point where your seat is confirmed, then you effectively have no rights if you are denied boarding or the flight is disrupted. EU261 (or UK261 if you're now leaving a UK airport!) is not a barrier.

Also on this point, you cannot ask a passenger to exempt themselves from EU261 - for example, in return for a cheaper ticket. Article 15 of the regulation prevents you from doing that - basically if a passenger accepts sub-par [or no] compensation, they can go back later and claim their entitlement. You can't therefore sell cheaper tickets with an opt-out from EU261, even though many consider that would be a worthwhile option - basically to give the consumer the choice.

On the topic of commercial standby fares, they used to exist very widely - British Midland had them across its domestic network. Marvellous they were too. They were about £25 one-way all-in back in the early/mid 90s.

There were two main reasons for these disappearing. The first was the advent of low-cost carriers who made £25 one-way fares pretty common place - you didn't have to take a risk on your travel plans to get one. If you could book in advance and have certainty for £25, most did. The second was the inversion of the yield management principles led by the LCCs - bookings got far more expensive towards the date of departure and the best deals were "reserved" for those booking early. Put another way, if the full fare was £150 and you had a standby fare of £25, for every last-minute passenger who might have been prepared to pay £150 but instead bought a cheapie £25 standby, you have to carry five more passengers to make up for the "opportunity cost" - the lost revenue - from that first one. It never happens, so therefore the standby fares dilute overall last-minute yields.

I can't think you'll see these back any time soon, even though there is no regulatory blocker to prevent it. I just can't see why any airline would put itself to the bother of doing it in today's world. And I'm sure you'd also have to get passengers to sign some disclaimer to say that you'd properly explained the conditions to them at the point of sale, to avoid creating yet another bandwagon onto which the EU261 claims people would no doubt seek to jump. The claims culture has done so much damage to the airline industry - heartily encouraged by that gob***** at Which? - that it is no wonder that relations between airlines and passengers are difficult.

I disagree for the very last point: the claims culture was also fed by the airlines when they were trying to save money when things went wrong. It is rumoured that EU261 was introduced because airlines overbooked and didn't offer sufficient assistance to the pax left behind

Correct. The tipping point was a major LCC running flights just once/twice a week to Mediterranean holiday islands, then doing a operational cancellation on those already on holiday there with subsequent flights sold out, and saying they would either refund the £30 fare or rebook on their "next available flight", which was several weeks away, leaving homeward-bound families stranded on the island. And their chief exec was then (inevitably) rude about them on television.

Errr...not really.

EU261 came about when the late Loyola de Palacio was Transport Commissioner and although it may not be helpful to land "blame", if this sits with any airline then it is Iberia. She had experienced her own problems with disruption including being stranded at Brussels one Friday night but was persuaded to take action after her Chief of Staff was bumped three times in fairly short order from flights. There is a good account of how this came about back in the history of PPrune here which doesn't need any re-telling.

LCCs weren't really into the holiday market back in 2004 in the way that they are now. The prevalence of the likes of Ryanair and easyJet in the holiday market was in its infancy.

I remember flying with a Delta standby air pass in 1984, but in those days load factors outside Friday & Sunday afternoon were around 50%. Very different in those days.