Here is some information I could find. Understand that (at least from my current understanding) Lightning science is still a field in great study. Lightning Sprites weren't confirmed as real till 90s sometime. Ball lightning isn't well understood as it is quite very rare. I forgot about positive lightning also, again most of these tid bits about lightning were documented past 1990, in positive lightning case the dangers weren't well known till a glider destruction in 1999... Here is the report from a wiki article on air safety http://www.aaib.gov.uk/cms_resources.cfm?file=/dft_avsafety_pdf_500699.pdf

http://wsx.lanl.gov/Publications/lightning_bolt.html

We are not experts on lightning#[2], and have only seen a few time-resolved lightning bolt photographs. Nevertheless, a few features stand out. The first thing to notice in frames 1-9 (before the bolt connects to the ground), is that the downward-propagating leader is always forked. At each point in time, one fork or the other will "survive", and be selected as the stroke meanders downward. There is an interesting propagating remnant in frames 6, 7, and 8, which looks like a "blob" of plasma. Multiple filaments in frames 9, 10, and 11 are observed to be helically intertwined, and the current channels are probably self-attracting. The return stroke in frame 12 was too bright, and caused a camera artifact near the top of that image. We did not count the seconds from the flash to the thunder, but the range to the bolt can be estimated by noting that the object at the bottom of the flash in frame 12 is a high-voltage electric transmission tower on the west side of the White Rock canyon, overlooking the Rio Grande river, and it is silhouetted in the flash. The tower is 50 meters tall, and the bolt was at least 1.5 km away. The field of view of the image is therefore approximately 800 meters vertically, and the leader is propagating downwards at a speed of 1x105 m/sec or greater. The current faded away slowly in frames 13-18, until it was invisible, without changes in position. This bolt did not exhibit later strokes, as is often the case. From analysis of these pictures, one can conclude that this lightning bolt had a "typical propagation speed" for its downward propagating "a -stepped leader"#[3]. The image is also available as an MPEG movie file at on the World Wide Web at http://wsx.lanl.gov/gwurden.htm. This work was supported by US DOE contract W-7405-ENG-36.

and

http://www.plasmacoalition.org/plasma_writeups/lightning.pdf

Each downward stroke is composed of a downward-moving “leader,” followed by an upward-moving “return-stroke.” The leader creates a conducting path between the cloud and ground and distributes negative charge from the cloud along that path; the return stroke follows the same path moving from the ground toward the cloud, distributing positive charge to neutralize the negative leader charge. The electrical current in a lightning flash varies from stroke to stroke as well as during each stroke. The return-stroke current rises rapidly to an initial peak of tens of thousands of amperes. That initial current pulse may be followed by a current of hundreds of amperes lasting for tens of thousandths of a second. The high return-stroke current rapidly heats the channel to a peak temperature near or above 50,000ºF, increasing the pressure in the channel to ten or more times normal atmospheric pressure. This makes the channel produce the intense light that we see and makes it expand, producing a shock wave that eventually becomes the thunder sound wave we hear in the distance.