Tail fin
 

Are there any airlines that light up their tail fin whilst flying at night?

Tonight as we finished our jog, I looked up and saw a plane flying in the dark sky above with a tail fin lit glowing red. We thought maybe it was a trademark design element of one of the airlines (though I've never noticed it before!).

I think many do at lower altitudes, but it'd be a waste of energy to do it at cruising altitudes.

I think MOST do at lower altitudes. I know JetBlue planes have the tailfins lit during approach to LGB (specifically, the approach to runway 30/12, which has planes passing directly over my in-laws' house), as do Alaska Airlines, Delta Connection and America West/US Air planes.

Yes. It is a great supplement to the strobes and position lights, which can easily blend in with lights on the ground. Also, it is tough to estimate distance to a point of light and much easier to estimate distance to a lighted surface.

Wow! You do learn something new everyday!

L

Makes me wonder how many other unusual lighting patterns there are on planes that in the right light and situation become UFOs

I can't think of what that might be, gail. Airplanes are required to display a red light on the left wing, a green light on the right wing, and a white stern light (visible only from behind, plus an anticollision system that is either a red rotating beacon or white strobes. Many planes have both the strobes and the red rotating beacon. Many small planes also blink their landing lights, just like the red and blue blinkers that you do not want to see in your rear view mirror. This is another means of enhancing visibility. The illuminated tail is not mandated by law but is a good idea from both an advertising and a safety standpoint.

Flying at night is wonderful, but pilots encounter many visual illusions when doing so. More than one pilot has changed course to avoid hitting Venus.