The Supreme Court of Canada has ordered the Canadian Transportation Agency (CTA) to take another look at a complaint about how Delta Air Lines deals with obese passengers.

The complaint was filed by Halifax-based passenger rights advocate Gabor Lukacs.

In 2014, Lukacs complained to the agency that Delta was in the habit of bumping larger passengers from full flights in the hopes they would buy a second seat.

Lukacs filed the complaint after obtaining an email in which a Delta representative responded to a customer concerned about a fellow passenger who needed additional space on the plane.

The transportation agency refused to investigate because Lukacs is not obese, saying he was not affected by the allegations.

Canada's one-person, one-fare policy requires airlines to cover costs on domestic flights for people who need additional seating. (Mark Lennihan/AP)

In September 2016, the Federal Court of Appeal overruled the agency and said it had not followed the CTA when it dismissed Lukacs's complaint.

Lukacs claims bumping obese or disabled passengers is "inhumane," and contradicts Canada's one-person, one-fare policy introduced in 2008.

The rule requires airlines to cover costs on domestic flights for people with disabilities who are accompanied by an attendant or need additional seating.

Lukacs thought he'd lose

"Once I was alone I began to cry," Lukacs said Friday, hours after the ruling. He had been teaching a class in his job as a math professor at Dalhousie University when he got the news. He said his students — who've been kept apprised of his efforts — gave him a round of applause.

Lukacs said he was pessimistic, based on the amount of questioning he faced from the justices when he argued his case. He said he expected to lose and was ecstatic when the majority of the court ruled in his favour.

"The decision vindicates my position that the Canadian Transportation Agency has been playing a game here," Lukacs said.

"They set up a test that I could never, ever meet and based on an impossible test tossed out the case. That is disingenuous, unethical."

Top court's ruling not unanimous

In ordering the CTA to take another look at Lukacs's complaint, the Supreme Court also amended the ruling from the Federal Court of Appeal. The lower court had instructed the agency to only look at the merits of the complaint.

"To refuse a complaint based solely on the identity of the group bringing it prevents the Agency from hearing potentially highly relevant complaints, and hinders its ability to fulfill the statutory scheme's objective," former chief justice Beverley McLachlin wrote for the majority.

The ruling was not unanimous.Three justices felt there was no reason to ask the agency to take another look at this complaint.

"L[ukacs] brought a complaint with no underlying facts, no representative claimants and no argument. His complaint is purely theoretical, his interest in the issues is academic, and the proposed suit does not constitute an effective and reasonable means of bringing the issue before the Agency."

The Supreme Court said the agency is still free to consider whether Lukacs should have standing to make the complaint.