The delays are in both directions of the line.
The backups begin near Route 123 and stretch about three miles toward the Turkey Run Park exit.
Traffic was at a standstill.
"Our policies got in the way of our values and procedures interfered in doing what's right,” United chief executive Oscar Munoz said.
A fellow passenger called it “the most outrageous treatment of a paying customer that I have seen in my two decades of flying.”
Traffic will get by on two of the three southbound lanes from 9 p.m. Saturday until 6 a.m. Monday.
Stray electrical current overheated a rail fastener, causing the rush hour mess — the third such incident in the past two weeks, Chief Safety Officer Pat Lavin said.
Amalgamated Transit Union Local 689 President Jackie Jeter said Metro management is seeking concessions that would reduce the workers' total wage and benefits package by $100 million.
The incident closed all northbound and southbound lanes of the parkway at Morningside Lane.
The artwork is designed to enhance each community's character at 21 stations, officials say.