TORONTO -- News that 16 international flights carrying passengers who were later diagnosed with COVID-19 have landed in Canada since June 29 may have taken some Canadians by surprise.

After all, aren't borders closed? Hasn't the near-universal response to the pandemic been for countries to encourage their citizens to come home and discourage everyone else from visiting?

Why, then, are flights still arriving in Canada from international destinations including Addis Ababa, Cancun and Charlotte, N.C.?

The answer: Discouraging something is not the same as stopping it.

Yes, Canada's border has been closed to most non-Canadians since March 18, and to most Americans since March 21. Yes, the orders enacting those closures are still in force – until at least Aug. 21 for Americans and at least July 31 for the rest of the world. And yes, the demand for international flights plummeted in the early days of the pandemic and remains low now.

But flying a plane into Canada was never banned. When WestJet and Air Canada announced that they were suspending all their regular international flights, it wasn't because the government forced them to. It was because they calculated that doing so would be best for their business, as there were simply nowhere near enough passengers to make flying the routes worthwhile.

Since then, both airlines have resumed flights between Canada and destinations in the U.S. and overseas, albeit at frequencies far reduced from the pre-pandemic era. Many foreign airlines are flying between Canadian and international airports as well. A scan of the arrivals board on the website for Pearson International Airport in Toronto found that seven international flights from three different continents were scheduled to arrive within a three-hour span Wednesday afternoon.

Those flights, like all arriving from outside Canada, are still subject to many restrictions. For one, they are only allowed to land at four airports – those in Vancouver, Calgary, Toronto and Montreal. Additionally, only certain passengers are allowed to fly into the country: Canadian citizens and permanent residents, citizens' immediate family members, diplomats and air crews. There are also exemptions for temporary foreign workers, some students, anyone delivering urgent medical supplies, and others whose purpose for being in Canada is deemed to be essential.

Everyone entering the country for a non-essential reason must self-isolate for 14 days. Not doing so is a violation of the Quarantine Act and carries a maximum penalty of a $750,000 fine and six months in jail, although the publicly known penalties that have been levied during the pandemic are much smaller.

The Public Health Agency of Canada (PHAC), which is tasked with following up with those who arrive in the country, has informed the RCMP of more than 21,000 cases in which they either could not contact the travellers or received what they describe as an "indication of non-compliance" with the Quarantine Act.

Nearly 1,500 of those cases were identified by the RCMP as serious enough to warrant a physical check-up, a PHAC spokesman said, and four resulted in fines.

It is not clear how many of the cases, check-ups or fines involved people who arrived in Canada by air. The spokesman said PHAC and the RCMP have been notified of 237 cases by the Canada Border Services Agency, which screens passengers at all entry points to Canada.

Similarly, although the government recommends that Canadians avoid all non-essential travel outside the country, it is not stopping anyone from leaving.

Border restrictions in some parts of the world may make it difficult for Canadians to get in, but other regions – including the nations of the European Union and some Central American and Caribbean countries – have made it clear that they are welcoming Canadians and other visitors.

There is nothing legally stopping any Canadian from taking a vacation to swelter in the sun in Jamaica, for example, by flying directly to and from Toronto, provided they self-isolate for 14 days upon their return.