The Icelandair jetliner had to be diverted to Edmonton, where fire engines were waiting on the runway - just in case. But the plane landed safely and normally.
An airport spokesperson says it appears there was some kind of mechanical issue with the plane, but they're still trying to figure out what exactly happened.
Passengers said the crew took the emergency in stride and kept everyone from panicking.
"The crew was calm and handled it very well," said one passenger, Kit Jensen of Denmark.
Passengers were taken to hotels for the night.