The US Department of Transportation (DOT) acknowledged that it had yet to levy any penalties in any of the dozen cases since May involving tarmac delays of at least three hours. Some investigations have been closed because they occurred under circumstances excepted by the tarmac delay rule, such as instances involving safety, security or air traffic control operations issues. In other cases, the tarmac delays violated the three-hour rule by only a few minutes, and DOT determined the carrier had worked to comply with the rule. Some carriers received warnings.Source: Travel Weekly; find article here>>.