For the second month running since the U.S. Department of Transportation introduced a new consumer rule on April 29, the largest U.S. airlines have...

The new aviation consumer regulation that allows the U.S. federal government to penalize domestic airlines with fines of up to $27,000 per passenger on flights that experience tarmac delays of more than three hours appears to be working.

For the second month running since the U.S. Department of Transportation (DOT) introduced the passenger-protection rule on April 29, the largest U.S. airlines have reported drastically lower numbers of tarmac delays exceeding three hours, without reporting any increase in the rate of flight cancellations. Canceled flights are not counted by the DOT as delayed flights, a quirk in the DOT’s statistical analysis of airline-service performance that industry observers believe various U.S. carriers have used to their advantage in the past.

The 18 largest U.S. airlines reported a total of three flights in June which experienced tarmac delays of more than three hours, compared with 268 flights in June 2009. At the same time, there was no increase in the rate of canceled flights, according to the June 2010 Air Travel Consumer Report released on August 10 by the DOT.

A long line of aircraft waits on a taxiway at Hartsfield-Jackson Atlanta International Airport to turn on to a runway for take-off. Hartsfield-Jackson is the world's busiest airport both for aircraft movements and for passengers

According to information filed by the 18 airlines with the Bureau of Transportation Statistics (BTS), a part of the DOT’s Research and Innovative Technology Administration, the only tarmac delays longer than three hours reported in June by the 18 airlines which file on-time performance with DOT involved three United Airlines flights departing Chicago’s O’Hare airport on June 18, a day in which the Chicago area experienced a severe thunderstorm.

None of the three United tarmac delays exceeded the three-hour limit by more than five minutes, according to the DOT, which says it is investigating all tarmac delays that exceed the three-hour limit.

June was the second full month of data obtained by the BTS since the new aviation consumer rule went into effect on April 29.  In May, the first full month, there were five reported tarmac-delay times of more than three hours, down from 34 in May 2009.

All the reported May incidents apparently involved one airline and a subsequent DOT investigation determined that four of the five May flights were misreported by the airline concerned.  The DOT says corrected data will be available from the BTS when the airline submits revised data.

According to the BTS data, the 18 U.S. carriers canceled 1.5 per cent of their scheduled domestic flights in June, a rate equal to the airlines’ 1.5 per cent cancellation rate of June 2009. The carriers posted a 1.2 percent cancellation rate in May 2010.

The new aviation consumer rule prohibits U.S. airlines operating domestic flights from permitting an aircraft to remain on the tarmac for more than three hours without deplaning passengers, with exceptions allowed only for safety or security or if air traffic control advises the pilot in command that returning to the terminal would disrupt airport operations.

However, international flights from U.S. airports – whether by U.S. or non-U.S. airlines – are not covered by the new tarmac-delay regulation, a situation that has been criticized by aviation consumer groups.

On June 22 passengers were held on a diverted Virgin Atlantic Airways flight at Bradley International Airport in Hartford, Connecticut for four hours in an aircraft that did not have air conditioning available; two passengers reportedly became ill and had to be taken off the aircraft for treatment.

Additionally, in previous years, tarmac delays as long as 10 hours for international flights at New York JFK created much of the momentum for the DOT to introduce a regulation limiting tarmac delays to a maximum of three hours before airlines must allow passengers to disembark.