Long time ago I remember reading about them on RyanAir but I can't find anything on their website?
So three years ago, RyanAir sort of implied they might do standing seats if allowed. The world looked on in horror, shock, half contemplated if they'd do it for one hour flights, and then it went away.
Except it didn't. Airlines have half-mentioned it since then, including both RyanAir and SpringAir.
Again, this is just talk at this stage, until it wasn't, when AirBus filed their saddleseat patent, which was almost standing seats. You perch on the seats instead of reclining. Here's the official patent.
A study in Malaysia then showed that on a 737-300, a standing cabin would lead to a 21% increase in capacity and drop tickets up to 44%.
And then this year, not to be outdone, Boeing filed a patent for an upright sleep support system on planes, which could in theory reduce the need to recline seats, and some argue could be combined with other formats to allow standing too. The more the merrier, perhaps?
While no airline has actually offered this yet, given the experiments in seating (see AirNZ's cuddle class) and the ever increasing demand to fit more people on flights for less money, many people (including that aforementioned study) predict standing class might not be that far away.
This was a publicity stunt by Ryanair. No such product exists and it is dubious it would be approved as safe by the Civil Aviation Authority.
It's worth noting that Ryanair and Easyjet are already close to the maximum number of people they can allow on board based on the size of the emergency exits on the aircraft they use. Therefore this product would not really offer them any advantage in terms of densification.