Researchers say it's another example of unintended consequences

The federal government enacted a new rule in 2010, penalizing airlines if they keep planes full of passengers stranded on the airport tarmac for extended periods of time.

The rule followed several highly publicized incidents in which passengers complained of being stranded for hours, with no food or water and with highly unsanitary conditions.

Government data shows that tarmac strandings are now fairly rare, but like many rules, this one may have had unintended consequences. A study by Dartmouth College and the Massachusetts Institute of Technology (MIT) finds more passengers now encounter other types of delays.

The study, supported by Federal Aviation Administration (FAA) National Center of Excellence for Aviation Operations Research (NEXTOR II), concluded that it now takes most passengers far more time to arrive at their destinations.

Significantly increased delays

"Overall, the rule is estimated to have significantly increased passenger delays, especially for passengers scheduled to travel on the flights that are at risk of long tarmac delays," said Vikrant Vaze, an assistant professor at Dartmouth's Thayer School of Engineering.

The rule requires commercial aircraft to take off or allow passengers to leave the plane no later than three hours after the cabin door closes at the departure airport. At the other end, passengers must be allowed to depart the aircraft no later than three hours after touchdown at the arrival airport. Airlines that fail to meet that requirement face hefty fines.

The researchers say the consequences of the tarmac rule could have been predicted. Now, when it is evident that a flight will not be able to take off on time, the airline is likely to cancel it before passengers can board, heading off potential fines.

When the flight is cancelled, the passengers must then scramble to make alternate travel plans, often delaying their arrival at their destinations.

Recent data contradiction

It should be pointed out that recent government transportation data shows just the opposite. As we recently reported, the FAA shows no three-hour tarmac delays occurred in July, while the month also experienced very low percentages for delays and cancellations.

The Dartmouth-MIT researchers say they studied actual flight schedule and delay data from 2007 before the rule was enacted, then compared these delays to those estimated for hypothetical scenarios with the rule in effect for that same year.

While the rule has been highly effective in decreasing tarmac delays, especially long delays, their research shows each passenger-minute of tarmac time saving is achieved at the cost of an increase of approximately three passenger-minutes in total passenger delays.

The researchers attribute these delays primarily to the increase in flight cancellations, resulting in passengers requiring rebooking and often leading to extensive delays in reaching their final destinations. The researchers say the tarmac rule should be tweaked.

"We concluded that a better balance between the conflicting objectives of reducing the frequency of long tarmac times and reducing total passenger delays can be achieved through a modified version of the existing rule," Vaze said. "This modified version involves increasing the tarmac time limit to 3.5 hours and only applying the rule to flights with planned departure times before 5 p.m.”

To cut the airlines a little more slack, the researchers say the penalty clock should stop when a stranded aircraft begins returning to the gate instead of when passengers are allowed to get off.