This article originally published at Helicopter crashes into kilometer-long slackline in Arizona, killing four.

The people who strung the line - which is used in a sport akin to tightrope walking - had filed an aviation safety notice, raising questions about the air alert system.

Federal investigators are examining if a slackline was properly authorized following the deadly helicopter crash near Superior that claimed the lives of four people on Friday, ...

Preliminary evidence indicated a slackline of more than 1 kilometer in length was strung recreationally across a canyon.

SUPERIOR, AZ (AZFamily) — The four people who died after a helicopter crashed east of the Valley late Friday morning have been identified by their family. “Many have heard about the unimaginable ...