Porter Airlines has extended the temporary halting of all of its flights by four more weeks, until June 29.

The Toronto-based airline announced last month that it would be suspending all of its flights as of March 21 until June 1 because of the novel coronavirus that causes COVID-19.

On Monday, the airline extended those shutdown plans by at least another four weeks.

"Our initial restart date of June 1 was something we believed was reasonable at the time," president and CEO Michael Deluce said in a news release.

"While there are many promising signs about how COVID-19 is being contained, it is also clear that border restrictions, government-imposed stay-at-home orders and bans on non-essential travel will remain in place for many regions through much of May and into June. This makes it difficult for people to travel, so Porter will continue aligning its approach with the public health response."

Like many airlines, Porter was hit hard by the dramatic reduction of air travel because of COVID-19. In addition to grounding all of its flights, the airline said it issued temporary layoff notices to most of its 1,500 staff members. The airline said it has been able to rehire some of them during the shutdown by applying for a new government wage subsidy program that covers up to 75 per cent of salary costs.