On-time arrival data skewed by airlines to meet own priorities

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On flights from Atlanta to Chicago O’Hare during the first half of this year, American, United, Frontier and Spirit each had average gate-to-gate times of between 127 and 129 minutes. Yet on-time stats for the four airlines were markedly different.

That variance points to a flaw in the Department of Transportation (DOT) system for calculating on-time arrivals: Airlines are allowed to set their own average gate-to-gate expectations — known as “block times” in industry parlance — and each carrier manipulates that expectation to accommodate its own corporate priorities, which can range from brand image to labor cost containment.

American, with an average block time  of 129 minutes, reached O’Hare within 15 minutes of its schedule 78% of the time. In contrast, Spirit, which also averaged 129 minutes on the Atlanta-O’Hare route, arrived within 15 minutes of schedule just 40% of the time.

Similarly, Frontier completed the route in an average of 128 minutes but arrived within 15 minutes of schedule — the metric the DOT uses to define on-time arrivals — just 49% of the time. United, on the other hand, flew from Atlanta to O’Hare in an average of 127 minutes, good enough for an on-time arrival rate of 71%.

As a result of these apples-and-oranges block times, passengers who attempt to compare on-time performance of various carriers when making a booking decision can in fact be basing their choice of a carrier on flawed assumptions about the DOT’s data.

On-time arrival statistics, along with cancellation numbers, are the most often cited performance indicators for airlines. Indeed, those figures are so important to airline customers that this summer Delta rolled out a pledge to its corporate clients: We’ll give you flight credits, the Atlanta-based carrier said, should we trail American and United over a calendar year in both measures.

But as the Atlanta to O’Hare figures suggest, operational times are just one piece of the complicated scheduling puzzle that ultimately determines an airline’s on-time performance. And low-cost carriers, faced with the most pressure to keep prices down, are especially challenged when it comes to scheduling.

“It’s a problem for all airlines, but I think the [low-cost carriers] really have to work hard at streamlining operations,” said Tulinda Larsen, an airlines operations analyst for Global Eagle Entertainment.

Data for the first half of this year, compiled by the aggregator FlightStats, show that on major routes flown by three major U.S. legacy carriers, the scheduling of block times was remarkably uniform.

FlightStats provided Travel Weekly with data for 103 routes between airports in the nine largest flight markets in the U.S.

Of those routes, 10 were flown by all three of the majors, whose overall scheduled block times on those routes averaged within a minute of each other. Actual flight times were also quite similar on those 10 routes, with United, the fastest, arriving at the gate less than 1% more efficiently than American, the slowest.

Out of the 103 routes compiled by FlightStats, Delta flew 37, and its average gate-to-gate time exceeded its planned block time on three routes. Southwest flew 46 of the routes, with its average gate-to-gate time exceeding its planned block time on just one route. Similarly, American, failed on that metric on just three out of 48 routes, while out of 38 routes, United never failed. (Due to the potential for statistical outliers, routes flown by a carrier less than five times were not included in the above figures.)

The low-cost carrier JetBlue also fared well with block time adherence, averaging longer gate-to-gate times than the scheduled block on just one of 18 routes between the major markets, its service from Burbank. Calif., to New York Kennedy.

But Spirit and Frontier struggled, with Spirit’s average gate-to-gate time exceeding its scheduled time on seven out of 14 routes and Frontier seeing that result on eight out of 12 routes.

The data also show, however, that even on the routes in which they routinely failed to meet their block expectations, the airlines were competitive as far as actual flight times.

Spirit averaged an aggregate gate-to-gate time of 135 minutes on the seven routes provided by FlightStats in which they failed, on average, to stay within their flight blocks. In contrast, carriers that serviced those routes and, on average, met their scheduled block times, averaged gate-to-gate times of 137.4 minutes. But they also, blocked more time — an aggregate average of 142 minutes between the seven routes, versus 130 minutes by Spirit.

On the eight routes in which Frontier, on average, failed to meet gate-to-gate expectations, its aggregated flight-time average was 147 minutes. That was slower — though by less than four minutes — than airlines that met expectations on those routes. However, Frontier scheduled an aggregated average block time of 141 minutes for those seven routes versus the aggregate average of 148.5 minutes that the other carriers scheduled.

Those tight block schedules contributed to an on-time percentage for Frontier of less than 69% in the first half of this year, well below Delta’s, American’s and United’s respective on-time percentages of 85, 79 and 77.

DOT online data do not show Spirit’s on-time stats, but FlightStats data shows that the airline had monthly on-time rates during the first half of the year that varied between a low of 54% in June and a high of approximately 76% in March and April.

Frontier Chief Commercial Officer Daniel Shurz said that part of the reason the airline underestimated some of its block times during the first half of the year was that it was implementing numerous new routes that didn’t involve the carrier’s traditional Denver hub. Frontier has since made some adjustments. For example, its block time for that Atlanta-O’Hare route has been increased from 119 minutes to 128 minutes. Such changes helped Frontier improve its on-time rate to 77.4% in August, he said.

Still, Shurz said that Frontier is not likely to increase scheduled flight lengths to the levels of the legacy carriers.

“We just don’t pad the schedules endlessly,” he said. “We are focusing on making our operations work more efficiently to get on-time arrivals.”

One issue that drives Frontier, as well as Spirit, to keep scheduled block times shorter is that pilots and crews are paid according to those schedules. Longer planned block times mean higher labor costs. And low-cost carriers can’t afford to pass on those costs to consumers.

In addition, said Spirit spokesman Paul Berry, scheduling shorter block times enables the airlines to operate more flights per plane. Ultimately, he said, that greater efficiency leads to cost savings, even if Spirit’s on-time statistics suffer a bit as a result. While Spirit wants to be on time, he said, it also doesn’t believe passengers are especially bothered by arriving at their destination 15 or 30 minutes late.

“We are much more focused on canceled flights than we are on delays,” he said.

Jim Hetzel, vice president of aviation and distribution for FlightStats, offered a similar analysis after viewing the data from the routes between major markets over the first half of the year.

“I just think there’s a lot of pressure for a low-cost carrier to maximize their fleet,” he said. “They’re trying to schedule tight. And their ability to perform against that flight scheduling isn’t matching up.”

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