UP Express trains are running between Union Station and Pearson airport again on Monday night, after a signal failure issue caused the line to shut down for several hours.

Metrolinx said a "major signal failure" near Weston was to blame for delays up to 90 minutes around 6 p.m.

Crews have since repaired the problem.

This is the first "major" failure of this kind on the line, Metrolinx spokesperson Anne Marie Aikins said.

"Any rail service can have a signal failure like this," she said. "Signals are there for a reason to keep the trains safe and operating efficiently."

Any riders who purchased a ticket but didn't use the train will get a refund, Aikins said.