The CO agent told me if I use a UA SWU upgrade on CO international flight, there is a significant charge for the lap child (10% of business class fare if the upgrade clears). So it would cost me additional $438 for a SWU upgrade for CO flight from ORD to DEL. Anyone heard this before ?
The CO Agent was correct in assessing you that 10% verbiage for the Lap Child however YMMV on whether the fee is collected or not on day of departure...
It is worth noting that the 10% rule applies in coach as well. It is also worth noting that CO charges the 10% based on the lowest fare available at the time of request rather than requiring 10% of full fare as some carriers do. This does mean that it is often advantageous to book it if you can find the discounted C fare available.