It's been six years now since the Department of Transportation introduced a rule that penalizes airlines with hefty fines every time they leave passengers sitting on the tarmac for more than three hours before departure or after landing on domestic flights.
At the time of the rule's 2010 implementation, airline executives warned that it would result in an increase in canceled flights, as carriers would simply call off delayed departures to avoid penalties.
Sure enough, studies found that in the first three years that the rule was in effect, airlines did indeed cancel more flights—especially on routes prone to delays.
But according to an audit by the Office of the Inspector General, the situation improved so much in the following 12 months that the agency was able to conclude, ultimately, that the tarmac-delay rule did not lead to an increase in canceled flights in the long term.
Not surprisingly, the rule did, however, help to speed up departures. The percentage of flights with tarmac delays of an hour or more fell by almost half after the rule was established; waits of more than two hours decreased by 70%.