Last October I put a client from Mississauga on the 6:15 a.m. Porter flight out of Billy Bishop, because she had a Saturday matinee at the Belasco and a dinner booked for eight, and because the fare was CAD 218 one way, which is about as good as that route gets when you buy eleven weeks out. She landed at Newark at 7:40. By 8:20 she was standing on the AirTrain platform watching a board tell her the NJ Transit Northeast Corridor line was suspended between the airport and Penn Station for weekend track work. Nobody at Porter had mentioned it. Nobody at the rental counter mentioned it either, and the taxi queue was forty minutes deep by the time she gave up on the train. She made the matinee by twelve minutes, having paid CAD 96 for a car she had not budgeted for.

That is the whole argument in one trip, and it explains why, when comparing flight options between Toronto – New York City, I now open two browser tabs before I open my usual search: one for fares, one for the MTA and NJ Transit service advisories pages.

What the advance-purchase calendar actually costs you

Airlines price the Toronto to New York corridor on scarcity, not on distance, so the gap between booking early and booking late is wider than on almost any other short-haul route out of Canada. On Air Canada and Delta out of Pearson, and on Porter and American out of Billy Bishop, the same Tuesday in March can run CAD 240 booked nine weeks ahead and CAD 610 booked nine days ahead, with United and WestJet somewhere in that band depending on how the corporate demand looks that week. That is a real spread, and it is the reason most of my clients want to commit early.

Here is what they get wrong. An advance ticket protects your fare, not your itinerary. MTA weekend closures are published roughly ten days out, sometimes less, and the shuttle buses that replace a suspended line add twenty to forty minutes to a trip that a subway map says takes eleven. On the 7 train between Manhattan and Flushing, on the L between Manhattan and Brooklyn, on the A into JFK, the pattern repeats often enough that I assume it will happen and price the trip accordingly.

The things I check before letting anyone pay for a nonrefundable fare:

• Whether the dates hit a planned closure on the line nearest their hotel, checked on the MTA site, not on a news summary
• Whether their airline’s change fee plus fare difference is smaller than the CAD 96 a stranded arrival costs in car service
• Whether they are flying into Newark, JFK or LaGuardia, since the replacement-bus problem is worse at Newark than at the other two
• How much of the trip is time-critical, which is usually less than the client thinks

Where flexibility earns its premium

If the trip is a funeral, a court date, a wedding, or a Saturday matinee, buy the flexible fare. A CAD 120 premium on a fully changeable ticket looks expensive until you are rebooking a CAD 610 walk-up at short notice because the L was closed and you missed the thing you flew down for.

But if the visit is loose, if the point is to wander and eat and see friends, the advance fare wins nearly every time. I had a couple from Halifax last month take the cheap nonrefundable at CAD 196 each way, hit a planned 2 train suspension on a Sunday, and simply spend the afternoon in the Village instead. Nothing was lost. The delay was the trip.

For anyone weighing this properly, checking flights between Toronto and New York City across a few weeks of dates tells you more than any single quote will, because the corridor moves daily and the airline that is cheapest on a Thursday is rarely cheapest on a Saturday.

I will not pretend there is one right answer here. The variable that settles it is how much of the trip depends on arriving at a specific address at a specific hour, and once you have written that number down, the fare decision makes itself. If nothing on your list is time-critical, buy the cheap ticket and treat a replacement bus as part of the day. If two or three things are, pay for the flexibility and stop checking prices after you do, because you can also see here for the current spread and it will only make you unhappy.

One more thing, since it comes up constantly. Canadians ask me whether their provincial health card covers them if a subway shutdown strands them overnight and they need a hotel. It does not, and the airline is not obliged to put you up for a delay caused by transit. That is a travel insurance question, not a fare question, and it is the reason I tell people to read the delay clause before the price.