Photo on the left shows the new painted bottom. The one on the right shows the old aluminum bottom.CLICK FOR LARGER.

You might be an airline nerd if this interests you. Warning: I am an airline nerd.

On the Twitterverse and Airliners.net, there were some questions around why American Airlines has started to paint the bottom of their new Boeing 737s. There was some speculation (and questioning if American is even really painting the bottoms), but officially from American:

“All 737’s have fluid discharge ports along the bottom Aft fuselage. AA has decided to paint the underbelly of the aircraft for aesthetic purposes and to prevent any contact of these fluids with the bare aluminum skin.”

Nothing too shocking, the bottoms have been painted to slow corrosion. I only hope that this is not a sign that American plans to keep this dated livery over the long-term. As I am sure you remember, the airline recently went into Chapter 11 bankruptcy, which would give them a perfect reason to get a new livery (even though I know there are a lot of American livery lovers out there).

Both photos taken by Drewski2112 at Boeing Field