Last month I flew from Denver to Frankfurt in Lufthansa. 747-400. Stuck in economy class unfortunately.

The seating configuration is 3-4-3. I pre-selected an aisle seat in the middle section with 4 seats. I think my seat was 51G or something like that. I was hoping the seat next to me 48F would stay empty, it was empty when I chose 51G. I figured worse case scenario, if someone was sitting next to me, I'd only have to get up for one person to get out from time to time, whereas if I picked an aisle seat on the "3" side, I might have to get up for two people.

I board the plane and take my seat in 51G. There's an older man 51E and his wife in 51D, but 51 F is empty. So far so good.

I wait anxiously for boarding to finish, which it does, then I hear them announce that they've closed the doors. Perfect! My strategy worked! Scored an empty seat next to me on a 10 hour flight!

There's no way anyone setting elsewhere is going to try to switch seats and slide into the middle there between me and the older couple. I figure I'm in the clear, I don't bother trying to mark the seat by putting my bag there or anything petty like that.

Plane takes off, and out of the corner of my eye I see the older couple having a conversation and they keep looking over at the empty buffer, 51F, that separates me from them. Then they get up, the guy steps out , and the woman slides all the way over into 51F next to me, so that they can have an extra seat between them. Come on. And she had really bad perfume on, and I was really miffed by this turns of events, but I figured there was nothing I could do.

So I just sat there for ten hours, while they actually alternated between who sat next to me in the DMZ of 51F, occasionally the guy would sit next to me while the woman tried to "recline" across 51D and 51E.

In their defense, when the one sitting next to me had to get up to go the bathroom, they didn't ask me to get up, they slid out the other way across their luxurious 3 seat paradise.

Here are my questions:

1. Was there behavior within the bounds of acceptable airplane etiquette, or does etiquette dictate leaving the buffer between you and stranger?

2. Should I have done anything differently other than sit there and stew for ten hours? If I had place a bag there first would I then have had "rights" to the seat for the whole flight? What about just a coat or a book?