Researchers propose tweak to three-hour rule for tarmac delays


Passenger rights activists lobbied for years for the US Department of Transportation to establish a “three-hour rule” for tarmac delays, with the goal of preventing grossly extended delays upon taxi-out or taxi-in. In this context, the rule has been unequivocally successful; long tarmac delays are down. But experts have, once again, called into question whether passengers truly are benefiting from the policy. Flight cancellations are up and researchers suggest that the overall impact of the rule has proven to be a negative for travelers.

With US airlines running at record-high load factors, a cancelled flight – especially late in the day – can mean a long wait for an available seat on another flight. And this raises an interesting dilemma. Which is worse – a few people being very badly delayed or more people being less delayed?

A new study out of MIT and Dartmouth University takes a unique approach to analyzing the rule by using data from 2007 (chosen for its similarity in overall schedule to 2013 – over two years after the rule was fully implemented) to compare what the impact to passengers would have been then had the three-hour rule existed. The findings are dramatic: the average delay for affected passengers – those on flights that hit the three-hour delay mark – more than double to a ten-hour average impact in getting to the final destination. This takes into account flight loads and schedules as well as re-booking time and onward capacity; it considers return flights getting canceled in addition to the flight that has the long delay. It is a much more holistic view of the impact than just the three hours of taxi time.

Rather than simply stop with the conclusion that the three-hour rule makes things worse for many travelers the researchers pushed forward, using the data already in hand to play out multiple simulations of other scenarios. Not surprisingly, the researchers demonstrated that delays later in the day are harder to recover from because there are fewer rebooking options available. The conclusion from this observation is that a variable rule becomes more valuable to the industry and the consumers, with the report stating:

[I]t becomes progressively more difficult to find recovery itineraries for passengers disrupted later in the day, indicating that there is value in exploring the effectiveness of a tarmac delay rule that stipulates a maximum tarmac time limit only for flights with planned departure times before a certain time of the day.

Similarly, the researchers considered tweaking the three-hour hard limit to other possible durations. By extending the limit by just 30 minutes the number of affected passengers declines by 60%, a huge impact. More significant, however, is that the increase in delay to all passengers drops by 71% at a 3.5-hour limit rather than three hours. It is still a scenario where everyone is, on average, delayed more than they were without the rule, but the impact is tempered with this adjustment to the threshold.


By combining these two adjustments to the rule the research model suggests that the average delay to every passenger increases by less than 15 seconds while the average delay to passengers with flights impacted by the rule drops from more than 10 hours to just over seven, a three-hour improvement.

“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,” says Vikrant Vaze, an assistant professor at Dartmouth’s Thayer School of Engineering. “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. Finally, in order to implement the rule more effectively, we suggest the tarmac time limit be defined in terms of when the aircraft begin returning to the gate instead of when passengers are allowed to deplane.”

Perhaps the most significant finding of the research is that it conclusively demonstrates there is not a “one size fits all” solution to mitigating delays and their impact on passengers. A hybrid approach – one which allows discretion for the airline to consider the overall impact to passengers rather than just what the immediate cancellation will bring – would benefit everyone. But the threat of a multi-million dollar fine per incident prevents such considerations from taking place.

Like many instances of passenger rights regulations this one behaves something like a pendulum; currently it sits at one extreme while prior to the three-hour rule it sat at the far side (exemplified by the now notorious “Valentine’s Day Blizzard” delay encountered by JetBlue passengers in 2007, which helped to spur the regulation).

Coming to a happy medium remains a wishful dream but at least there is some real data to demonstrate what that should look like rather than a guess of three hours.