Air Canada flight AC-549 to Vancouver was grounded overnight.
The cabin lost pressure and the oxygen masks dropped down after a problem linked to an air conditioning unit.
The flight was going to Vancouver from Newark, New Jersey but had to be diverted to Toronto.
The airline says in a Twitter post that Flight AC-549 landed without incident.
AC549 landed normally YYZ w/o incident due to pressurization problem w/ AC unit. Arrangements made for customers to continue to YVR asap.
— Air Canada (@AirCanada) January 30, 2016