VANCOUVER -- Domestic passengers passing through security at Canada's four biggest airports will have their temperature checked as part of a screening process made mandatory by Transport Canada.

The federal agency requires passengers be screened at Vancouver International, Calgary International, Toronto Pearson and Montreal-Trudeau International as of Thursday.

The temperature checks were first announced in June. Transport Minister Marc Garneau said international passenger checks would be first, starting at the end of June, then the four largest airports would start screening domestic passengers by the end of July. 

Passengers will be screened as they pass through security, a statement from Vancouver's airport said.

Transport Canada also requires the Canadian Air Transport Security Authority (CATSA) to screen at employee security checkpoints.

The update comes as dozens of flights are flagged across Canada for potential exposure to COVID-19.

Last week, the federal government said passengers on at least 30 flights in the country had travelled with at least one confirmed case of COVID-19 onboard. 

Ottawa flagged nine domestic flights and 21 international flights at the time.

And earlier this week, B.C. health officials noted another five flights into and out of the province.

Those flights were between July 13 and 22, and involved YVR and the Kelowna International Airport.

The flights were either from or to Montreal, Edmonton, San Francisco and Mexico City. Details here

Those who've been on one of the affected flights are advised to monitor themselves for signs of symptoms for the next 14 days.