How electrician workers connect high-voltage cables together when the cross from a high mountain to lower inland?

People who string power lines are called linemen. Helicopters are used to pull cable. Something the size of a Hughes 500 can do the work. They can pull 4 miles of cable in under an hour. Pretty amazing to watch.

Apparently, they are using drones to do this work on some projects.

They build electric transmission lines down the side of a mountain.  

https://www.recorder.com/Power-line-proposal-could-reopen-remote-Vt-land-debate-9598159#lg=1&slide=0

Helicopters...……….