Originally Posted by
MSPeconomist
It's interesting that it costs more to upgrade from V class than E or X. It's furthermore surprising that you can upgrade at all from an E class DL ticket.
Complimentary upgrades from E fares are not processed by the system, but E is another fare class like the rest and this is how the KLM departure system sees it. DL doesn't have any public terms and conditions about upgrading with Cash + miles out of AMS, so I guess they don't take into account the domestic E fares restriction.