What is the Plane icon for?

[Artic7]

This Icon appeared a few days ago,when i click on it its goes through any current windows i have open.
Anyone know where it has come from???
Thanks Steve

 

[MacRS4]

The one on the left? It's for Airmail I think.

 

[Artic7]

The one on the left? It's for Airmail I think.

Yeah it is.....what a Div,forgot i had installed that!!! Thanks