"Complementary seats"?
 

Today I flew LHR-HEL in Business, my first time in an AY flight, but it left me with a small question. The Business cabin had several seats with signs saying, "Complementary seat, Enjoy!".

Some of these seats were actually unoccupied.

I couldn't figure out what the sign might possibly mean. Unfortunately I was too sleepy to ask one of the FAs while still on the plane, and managed to collect my thoughts only later in the lounge.

So, if you know, please tell me!

They don't sell the middle seat in C. Sometimes when the flight is unsold they upgrade few people. In those cases I have witnessed that they rather reroute some people than upgrade someone to the empty middle between two other upgraded fellow passengers.

Wow, "don't sell middle seats", I would not have thought that such a carrier existed! I am impressed.

So the signs could be in the spirit of "Here is an empty middle seat next to you with our compliments, enjoy!" :)

LH and OS does it in European C - nice that AY joined them! (of course the wording is a bit clumsy, but it's the empty seat that counts!)

This is standard in short-haul C among most European carriers.

It seems that I'm less and less able to make comments in English. Please read unsold as oversold.

Quite a lot of airlines do this in Europe, it does make a difference.