Beginning January 31, all four major Canadian airlines (Air Canada, Westjet, Sunwing and Transat) have agreed to temporarily suspend all flights from the Caribbean, Mexico and Central America for 90 days. The suspension is currently scheduled to end April 30; while most COVID situations change as conditions unfold, I would be surprised to see this end much earlier.
This is obviously going to affect a lot of travel plans, whether vacation or otherwise. Affected travellers will have to find other ways to get home, but the good news is that one-way repatriation flights are already being scheduled throughout the next two weeks. Below, I've collected the airlines' various plans for this, with contact info, as well as a few other bits of useful information.
Be aware that the new quarantine requirement for flight arrivals into Canada will go into effect "as soon as possible". Transport Minister Omar Alghabra told a CBC interviewer on January 31 that this may be as early as February 4th.
Air Canada are suspending all regularly-scheduled flights to and from the affected destinations, but will be offering several one-off repatriation flights from most affected areas. They've published a detailed list of flights here, check back for updates as the situation unfolds.
If you've got an Air Canada vacation package scheduled during the affected period, call Air Canada Vacations (not Air Canada) at 1-866-529-2079, or your travel agent, to request a full refund, rebook for future dates, or request a future travel credit.
All southbound flights have now been suspended, but Transat will continue to operate flights northbound from these destinations for two weeks from January 31 to February 13th. View a list of these flights here on Transat's website.
Note that many passengers currently at destination will be automatically rebooked, in order of departure date, so you'll want to stay on top of your email to keep an eye out for any changes.
Anyone with an upcoming Transat vacation package scheduled for the affected time period will receive an automatic refund, you don't need to request it. That said, personally I'd keep an eye on your credit-card statement to ensure this hasn't gotten lost in the shuffle, but expect that it might take a few days or more for them to get through what will be literally thousands of refunds.
If you're currently at destination and need to get home, Sunwing will make arrangements to fly you back to Canada sooner, with advance notice to ensure any COVID-19 testing requirements can be met before departure. You can contact the local Sunwing representative at your hotel, contact Sunwing via the Sunwing App, or call 1-809-466-2525.
If you've got a Sunwing vacation package scheduled during the affected period, call Sunwing or your travel agent to discuss a full refund.
While they have already suspended all southbound flights to the affected destinations, WestJet will continue to operate flights northbound from these destinations for two weeks from January 31. Guests who need to return to Canada should get in touch ASAP; if you booked direct with Westjet, contact them here, while if you booked with a travel agent or online service, that's who you'll need to call.
Continued updates can be found in the "Travel Advisories" section of Westjet's website.
If this doesn't cover your situation
Note that many passengers will be able to book return flights through the United States, though you should be aware that unlike many countries including Canada, American airport and customs procedures don't treat transit passengers separately from people whose destination is the United States, so you'll need to be eligible to enter the US on that basis.
You should also be aware that the Biden Administration has ordered the relevant agencies to prepare to enact a quarantine and testing requirement for all arrivals into the United States, and the details of this will presumably be announced in the coming days. The point is, be aware of what's currently happening on that count before you book, to avoid any complications or surprises.