Size of Object(s): I can't really say the size because it was hard to tell being in a plane, size is distorted from that perspective. But judging from the distance and size, I would say it had to be bigger than a car and maybe bigger.
Distance to Object(s): Plane was not too high. but it was slightly below the plane. 20K?

Appearance / Description of Object(s)
I can't really say the size because it was hard to tell being in a plane, size is distorted from that perspective. But judging from the distance and size, I would say it had to be bigger than a car and maybe bigger. I could clearly see it and the plane was staying clear of the cloud. But it simply looked like a ball of electricity with out any sparks or lightning. It did pulse slightly but not much. It had mass because it could go in the cloud and come out.

Description of Area / Surroundings
In the Air.

Full Description & Details
I was on my way home from Belize on the last leg of my flight (Continental) from Houston to Salt Lake City. It was at dusk and there were some gigantic storms in the area. The plane was flying around this huge round thunderstorm cloud (the ones you only get in summer with increadable energy). I was sitting in the window seat looking north east. On the side of the cloud I noticed this ball of light. It looked like electricity but with no sparks. It did not move a lot, only slightly and sometimes swayed into the side of the cloud but then came right out. I really could not understand what I was seeing, because I though it would disappear or disapate, but it never did. It was an interesting experience because the skies were clear. Again these were those big round summer storm clouds that really were putting down a ton of lighting below, but it was not over cast at all. So the plane just followed the circumfrence of the cloud to miss the storm. I watched the ball of light the whole time. It never left the cloud, and it was the planes progression that finally ended my viewing of the light.

Can sighting be explained as any conventional man-made or natural object?
I thought at the time it could be static electricity, but not stationary for 30 minutes, defineity not a balloon.

Personal Background
I am an archaeologist with a MA. I will be doing my PhD research soon.

Views on UFOs, before and after sighting
Ambivalent, I watched some TV shows.

Reported Sighting? No
Location: Pocatello, Idaho, USA
Age: 33