A new study by a team of aviation consultants, which claims the government’s new tarmac delay rule will cost the flying public $3.9 billion during the next two decades, is making waves in the aviation industry and beyond.

The Transportation Department yesterday issued a rare rebuttal, in which it called the study “questionable.”

The numbers used by the consultants, it said, were “far too narrow” to yield defensible conclusions about future airline trends. “Further,” it added, “the data reported in May 2010 does not support the industry consultants’ claims about rising numbers of airline cancellations.”

Surely the analysts must have known they were stretching things a little when they based their conclusions on one month of cancellation data. So why do it?

Maybe it was the money.

Some observers have suggested, and others have reported, that the airline industry funded this study. They have good reason to be suspicious: The study’s conclusions reflect the industry’s predictions before the new tarmac delay rule was enacted.

As one commenter on the Chicago Tribune site noted,

I read this story and had to laugh. A ‘study’ by a couple of airline consultants taking one month of data and extrapolating it over many years. The results just happen to echo what the airlines said would happen prior to the rule being implemented. Gee, I wonder who funded the study?

I asked Darryl Jenkins, one of the researchers, who paid for the study.

“Done in house at our own expense to promote our web sites,” he told me in an email. “A lot of fun.”

The other consultant, Joshua Marks, has contracted with airlines on previous projects, according to his site, although it’s unclear if the airline industry or its lobbying arm, the Air Transport Association, had anything to do with this project.

I’m willing to take Jenkins at his word when he says the airline industry didn’t fund this work. What’s more, I agree with many of his conclusions — notably, that the three-hour rule is just too onerous to be practical.

Perhaps the “who paid for the study” question is the wrong one to be asking. Maybe it should be the other way around. If Jenkins and Marks had never received any airline money, either indirectly or directly, would they have undertaken this study?

I think we all know the answer to that question.

(Photo: Francois Roche/Flickr Creative Commons)