On a flight from Melbourne to Newcastle today, I built some support for cyclomatic complexity into Complexian. It's not exposed via the Ant task or the main method yet, but the internals is working fine. I was pretty satisfied with the results of 45 minutes worth of coding.
Kent Beck and Erich Gamma famously wrote JUnit together on a plane trip too. There's something about the confined space and lack of other options (like phones for example) that causes you to focus on the task at hand. I wonder how much value you could get out of sending some members of your team on random flights together purely so they could pair on some interesting code.
Do you have any mile high code that you've created?