About 15 years ago, when my wife had status with AF, we wanted to use her points to upgrade from to BOS to the UK but there was no availability.

While waiting to board, there was an announcement with about 8 passengers asked to report to the departure gate staff. Upon arrival and staying out surnames, we were each handed an envelope with a short notice stating that we were being offered an upgrade and if we accepted the offer, we were requested to just nod or state "yes", that is, not to discuss that we had been upgraded.

Of course, we were very happy to do our best Noddy impressions just in case