Was on a DL codeshare/KLM metal int'l flight last week. A FA onboard our 777 went to EC customers with an iPad and started selling upgrades before takeoff. It was actually kind of aggressive. We thought no one would buy because it was around 500 Euros, but one man did. The FA then went into coach trying to sell an upgrade to the now-vacated aisle EC seat! And she found a buyer! Incredible. Never seen that before.

She didn't ask everyone; perhaps just Flying Blue members. It was interesting to watch...