On a recent trip from Vancouver to Paris, I called a week or so before our flight and asked about upgrades available to Economy Plus for I and my two companions using miles and was told there weren't enough upgrade seats available to upgrade all three of us. Two days before our return to Vancouver, I received an email from Air France offering an upgrade for each of us for $380 to Economy Plus or $555 to Business Class. I responded that I would take the upgrade to Business Class and we all came home in comfort from Paris to Vancouver. We had purchased the lowest fare class available in Economy for $620 roundtrip and we were still offered the upgrade, so I have to think that my call asking about an upgrade before our trip may have flagged us for the offer as a potential customer willing to pay for an upgrade.