Ottawa-bound Air Canada flight forced to return to London

An Ottawa-bound Air Canada flight declared an emergency and returned to London's Heathrow Airport Sunday after its air conditioning system malfunctioned.

Flight AC889 was already about three hours behind its scheduled departure time and had just taken off when the pilot decided to turn back, said Air Canada spokesman Peter Fitzpatrick. 

The emergency was declared only so the Boeing 767 could get priority to land quickly at Heathrow, said Fitzpatrick, and not out of safety concerns.

All 209 passengers arrived safely and will depart again Monday, he added.