Originally Posted by
thesun
... More relevant to UA, I'm under the impression that the extenders simply are stored on the aircraft? The "must pre-reserve" response that they got is a bit surprising to me. .....
Likely more bad info from that site
This is what UA says
If you do not require two seats but require a seat belt extension, you may ask for one from a flight attendant on board. You are not allowed to bring or supply your own seat belt extensions.
*The average length of the seatbelt extension is approximately 25 inches. As the seat designs on our aircraft vary, it is possible that the seatbelt extension presented on your flight provides less than 25 inches of additional coverage. Regardless of the actual additional length the extension provides, if you do not meet the first criteria listed above when using the extension provided on your flight, it will be necessary for you to purchase an additional seat or an upgrade, where available.
Now realistically there are a limited number on a flight but i concerned mention to GA/FA on boarding and I'm sure additional ones can be found.