Airlines are warning of cancellations and delays for travellers who are heading to southern U.S. states that may get the brunt of Tropical Storm Isaac.

With travel advisories in effect, travellers are being asked to check the status of their flight before heading to the airport.

Foreign Affairs has issued a warning of its own, urging Canadians to avoid non-essential travel to the northern coast of the Gulf of Mexico, from Morgan City, La., to Indian Pass, Fla.

WestJet issued a travel advisory for people heading to Miami, Fort Lauderdale and Fort Myers in Florida, while Air Canada’s advisory is in effect for travellers to Cuba, Jamaica, Miami, Fort Lauderdale and New Orleans.

On Sunday, most flights between Miami and Pearson were cancelled.

According to its website, WestJet and WestJet Vacations offer a “hurricane travel promise,” meaning travellers are eligible for flexible exchanges and refunds if their flight is affected by a hurricane or tropical storm advisory.

Air Canada is allowing affected customers to rebook flights without penalty, space permitting.

Isaac passed the Florida Keys overnight and is on course to strike the Gulf Coast states as early as late Tuesday night on the eve of the seventh anniversary of Hurricane Katrina. Forecasters expect Isaac to strengthen into a Category 2 hurricane before it makes landfall somewhere between the Florida panhandle and New Orleans.

With files from The Associated Press

@ChrisKitching is on Twitter. Don't forget, for instant breaking news, follow @CP24 on Twitter.