Please note I put "study" in quotes, because this is a story about what the Department of Transportation has to say about a study of one month's statistics of the effect of the new tarmac-delay rules. DOT fired back after two consultants concluded that airlines canceled far more flights in May than they did in May 2009 because of the new rules, which call for heavy fines if a plane is stranded on an airport ramp for more than three hours. This was just the kind of unintended consequence critics of the new regulations (i.e. airlines) warned us about -- it it's true, of course.
But DOT retorted with a statement, pointing out that one month's record for flight cancellations is not a good measure of the effect of the rules on airline operations. The consultants may be right, but they can't prove it -- yet. Wait for the end of the summer, and into the fall, and a serious analysis can be done. Read more about this here.