Start or open an existing google doc. Select the file menu and you should see the option for "New Airplane" under "New Document".

Excellent!

Haha, another April Fools, how many can Google do this year?

For those who can't see it yet, I've published the Document it creates http://docs.google.com/Doc?id=dfx7r7qn_209gvb32fdw

http://documents.google.com/images/GoogleAir.gif

Another one:
http://www.google.com.au/intl/en/gday/index.html

Hmm, I don't have the Airplane yet. Unless it's an April Fool's by you... :)

Philipp:
http://blogoscoped.com/forum/127783.html#id127786 (check the image's URL)

I don't have the airplane here either, but the image is hosted on a Google domain.

Google Docs, an airplane? I'm sure the real April Fool this year had to be "Clippy", but Tony & Philipp have unveiled it too early.

I don't have it either.. :/