Airline on-time performance, measured by the percent of 

flights arriving at their destination on time, has attracted 

growing interest in recent years as the number of air travelers has increased. Figure 1 provides a graph of the percent of 

U.S. major air carriers’ domestic flights arriving on time1 from 

January 2001 to December 20102. The time series data in the 

graph exhibits strong seasonal variation, which masks the 

underlying trend. 

Seasonality of the on-time arrival data can be viewed separately. One way to observe the seasonal patterns in the data, 

unaffected by the impact of changing long-term trends, is to 

1

 The percent of on-time flights is calculated as the number of flights 

arriving at their scheduled destinations less than 15 minutes after their 

scheduled arrivals, divided by the total number of scheduled operations. A 

scheduled operation consists of any nonstop segment of a flight. 

2

 These data are reported on the BTS key transportation indicators 

webpage http://www.bts.gov/publications/key_transportation_indicators/ as 

of Mar. 31, 2011.

calculate the monthly seasonal factors3—as shown in figure 2. 

Such cyclical increases and decreases can suppress or magnify the underlying trend, depending on if they are in synchronization or out of synchronization with the direction the overall 

trend is taking. For example, growth in overall on-time arrivals 

may actually be masked if a seasonal decrease skews the 

number of on-time arrivals downward. Conversely, an increase 

in overall on-time arrivals can be magnified by a seasonal 

increase. Decreases or leveling in the overall trend can also 

be similarly masked by seasonal fluctuations. 

3

 Seasonal factors estimate the effects that happen in the same month 

with the same magnitude and direction every year. These seasonal 

factors are additive and reflect movement away from the underlying trend. 

Positive factors indicate higher than average on-time arrivals (the original 

series is greater than the trend), and negative factors indicate lower than 

average on-time arrivals. 

Transportation Trends in Focus

RITA Bureau of Transportation Statistics

August 2011

Aviation On-Time Performance Trend Stable for Past 2 Years

By Peg Young, Ph.D.

About the Transportation Trends in Focus Series

The Transportation Trends in Focus series reports on 

the underlying trends in key transportation data. Using 

a variety of statistical analysis techniques, these reports 

examine recent trends, seasonality, and pattern shifts 

that the data reveal. This report looks at recent trends 

in monthly on-time performance of the U.S. major air 

carriers.

“Seasonality is the systematic, although not necessarily 

regular, intrayear movement caused by the changes of 

the weather, the calendar, and timing of decision, directly or indirectly through the production and consumption 

decisions made by the agents of the economy.”

S. Hylleberg. 1992. Modelling Seasonality. New York, 

NY: Oxford University Press.

Figure 1: U.S. Major Air Carriers Domestic 

On-Time Arrivals (percent of total scheduled domestic 

operations), January 2001–December 2010

100

90

80

70

60

50

40

30

20

10

0

Jan

2001

Jan

2002

Jan

2003

Jan

2004

Jan

2005

Jan

2006

Jan

2007

Jan

2008

Jan

2009

Jan

2010

On-Time (%)

SOURCE: U. S. Department of Transportation, Research and Innovative 

Technology Administration, Bureau of Transportation Statistics, available 

at http://www.bts.gov/publications/key_transportation_indicators/ as of 

Mar. 31, 2011
BTS Transportation Trends in Focus

2

As the histogram shows, the seasonal factors exhibit a distinctive pattern—typically higher percentages of on-time arrivals 

in the spring and fall, and lower percentages in summer and 

winter (attributable to increased travel and severe weather). 

Once the seasonality is removed from the data, the long-term 

trend of on-time arrivals becomes more obvious. Figure 3, 

which compares the actual data to the underlying trend, indicates a significant decrease in on-time arrivals in the month of 

September 2001. The trendline also indicates a decline in ontime arrivals from 2003 through 2007. However, the trend of 

on-time arrivals rose in 2008 before becoming relatively level 

in 2009 and 2010. The seasonality of the data tended to mask 

the level trend over these last 2 years. 

Figure 2: Monthly Seasonal Factors for U.S. Major 

Air Carriers Domestic On-Time Arrivals, (expressed 

as percentage point differences relative to the trend), 

based on data from January 2001 to December 2010

Jan Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec

0

2%

-2%

-4%

-6%

-8%

-10%

4%

6%

8%

10%

Deviation from trend

(percentage points)

SOURCE:U. S. Department o f Transportation, Research and Innovative 

Technology Administration, Bureau of Transportation Statistics, special 

tabulations, December 2010.

Figure 3: U.S. Major Air Carriers Domestic 

On-Time Arrivals (percent of total scheduled domestic 

operations)—Actual and Underlying Trend, January 

2001—December 2010

% on-time arrivals (actual)

% on-time arrivals (trend)

100

90

80

70

60

50

40

30

20

10

0

Jan

2001

Jan

2002

Jan

2003

Jan

2004

Jan

2005

Jan

2006

Jan

2007

Jan

2008

Jan

2009

Jan

2010

On-Time (%)

SOURCE:U. S. Department o f Transportation, Research and Innovative 

Technology Administration, Bureau of Transportation Statistics, special 

tabulations, December 2010.