Originally Posted by Aviatrix

You seem to have a very narrow definition of what "standby" means. "Standby" doesn't necessarily just mean "standing by at the gate". The airline I used to work for had standby fares which could be provisionally reserved from 24 hours before departure and were subject to final confirmation at check-in.

KLM already has a system of day-of-departure upgrades at airports with KLM-run lounges - your upgrade gets confirmed in the lounge unless there are fewer than two seats left in Business Class in which case you are provisionally upgraded subject to confirmation at the gate once check-in has closed. This system could be widened to other airports, or - if there was a 24 hour helpdesk - passengers could request upgrades by phone on the day of departure which would then be confirmed at check-in. It really shouldn't be that difficult to put a system into place which would allow last-minute upgrades without having to cause aggravation for gate agents.