What loss? First of all...selected offers would mean that these upgrades would only be available at a certain time before departure. And, of course, only if you have availability. It's about managing unsold products. This is what the web@wards are all about, for instance. Get more economy passengers to pay mor, and you make more money.

I would make the offers targeted, though,and use the database to find the people most likely to buy this upgrade. This means looking at people who have already bought the ticket, or who is buying last minute.