What is the length of lightning bolts?

Dear Tom,
What is the length of lightning bolts?
— James Torrinson, Chicago
Dear James,
The National Lightning Detection Network, or NLDN, operated by the Vaisala Group, measures the lengths of lightning bolts by utilizing a very high-resolution, three-dimensional detection system that records the emission of flashes in the very high-frequency range. The NLDN has been in place since the early 2000s and has generated some astounding information about the length of lightning bolts.
Meteorologist Ron Holle, a lightning expert with Vaisala, tells us, “The network has measured quite a few flashes over 100 miles long; our current record is 120 miles from a flash that shot from Dallas (Texas) to Ft. Worth. … I don’t think we would have expected that, but there it is!”
The National Lightning Detection Network has generated some astounding information about the length of lightning bolts.