|This joke never gets old.|
That's right; lanterns, of the Chinese variety.
TUS, however, concludes the lights are not lanterns of the Chinese variety. They state (emphasis theirs):
I don't know about alien space ships, but those are definitely not Chinese lanterns. Don't even try to go there, skeptics. That's a triangle!
First, let's have a look at the video of the incident in question:
Update 12/9/2013: The video originally embedded above has been removed from YouTube. As of this writing Texas UFO Sightings have another version embedded on their blog, but you can also download the video directly from MUFON.
Let's talk about why these lights are very likely Chinese lanterns. They have the same color as lanterns, they drift through the air like lanterns, and a witness can be heard to mention "it looks like little lanterns.. like little balloons." They also look just like another video of Chinese lanterns at night.
In other words, after applying the rigorous Duck Test to this footage, we arrive at a simple conclusion: Chinese lanterns.
But TUS also has this to say on the matter (via YouTube comments):
I would agree that these lights are a triangle. Of course, any three non-linear points, such as three points of light, can form a triangle. Over the span of the video their relative distances change, and so the triangle itself changes. This is the sort of behavior you would expect from three separate festive candle balloons from China floating across the night sky.
But most importantly, these lights do absolutely nothing that could rule out Chinese lanterns. For example: they don't do any crazy aerial maneuvers, the triangle doesn't block out any other lights (which would suggest a structure), they don't change colors, and they don't play this song.
All that said, and with all due respect to Texas UFO Sightings' conclusion, this also doesn't rule out some sort of craft. These could very well be some phenomena not yet understood by mankind.
But while we're testing for ducks, I'd also like to argue we should keep it simple.