Harriet Baskas Travel writer

If you board an airplane and take up more than one seat, must you pay more than one fare?  In North America, the answer will soon depend on whether you're traveling in Canada or in the United States.

On January 10^th, the Canadian Transportation Agency (CTA) took a stand on how much some airline passengers must pay to sit. You can read the official press release here, but essentially, the agency ruled that Canadian airlines (Air Canada, Air Canada Jazz, and WestJet) must let people with severe disabilities fly with a personal attendant at no extra charge. Next January, when the ruling goes into effect, the same "one-person, one-fare" policy will be applied to "clinically obese" air travelers who cannot fit into one seat.

A similar ruling has been in force for years on Canadian trains, buses and ferries. Now Canadian airlines have one year to figure out how they will comply. And even if you don't plan to travel in Canada anytime soon, you should pay attention to what happens.

I will. ("Seatmates of size" is a hot topic at the Well-Mannered Traveler headquarters.) Disability rights organizations in the U.S. will certainly be keeping tabs. And so should anyone who is, or has been squeezed in next to, a seatmate of size. Of course, you can be darn sure U.S. carriers will be watching what happens up north. Currently, most of them charge, or reserve the right to charge, for that second seat.

Here's some of what's at issue:

According to Jadrino Huot, spokesman for the CTA, the new ruling is a human rights issue and "does not apply to air travelers who are merely 'uncomfortable' on an airplane. It's not a matter of personal preference or a matter of personal discomfort. It's a matter of need and only addresses persons with severe disabilities."

On the face of it, the policy seems straightforward and an important precedent-setting victory for disability rights organizations. But airlines and well-mannered travelers have a lot of questions.

For example, the CTA ruling will not apply "to those who want to travel with a companion for personal reasons or people who require caregiver assistance on the ground but not on the plane." But who will determine what sort of assistance a traveler truly needs?  Will an airline take a passenger's word for it, conduct some sort of test or require a note from a doctor?

When it comes to making room for large passengers on Canadian flights, the issues seem even more complicated. The CTA's ruling states that the decision "does not apply to persons who are obese but not disabled as a result of their obesity." But it also says that Canadian air carriers must apply the one-person-one-fare rule to passengers "determined to be functionally disabled by obesity for purposes of air travel."

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Here too, definitions will become very important. What makes a passenger obese enough to be "functionally disabled for purposes of air travel"?  Who will make that determination?  Will a letter from a doctor be required or will gate agents have to "eyeball it" or ask a large passenger to perhaps step on a scale so BMI (body mass index) can be calculated?

Or will the Canadian airlines study Southwest Airlines' policy, which the CTA notes "screens for entitlement to an additional seat by determining whether a person can lower the seat's armrests."

Ah, there's the rub.  Southwest spokesperson Brandy King says in the United States, the Department of Transportation’s position is "that the purchase of a single ticket offers the use of a single seat." Southwest Airline's "Customer of size" policy sets the armrest(s) as the "definitive boundary between seats."  If a passenger fails the armrest test (i.e. cannot sit comfortably with the armrest down), the airline reserves the right to charge that person for an extra seat. (If a flight is not full, Southwest will refund that extra fare. King says that happens 97 percent of the time.)

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