A lightning "megaflash" that zipped across five U.S. states has set a new record for the longest ever detected.

One bolt of lightning covered a horizontal distance of 515 miles during a 2017 storm. A re-examination of satellite observations revealed the record-setting megaflash.

The 2017 “megaflash” stretched from eastern Texas to near Kansas City — a distance that would take at least eight hours by ...