Cancellations - The reporting carriers canceled 1.7 percent of their scheduled domestic flights in December 2015, up from both the 1.4 percent cancellation rate posted in December 2014 and the 1.0 percent rate in November 2015. For the full year 2015, the reporting carriers canceled 1.5 percent of their scheduled domestic flights, an improvement over the 2.2 percent cancellation rate in 2014.

Tarmac Delays - In December, airlines reported 11 tarmac delays of more than three hours on domestic flights and three tarmac delays of more than four hours on international flights.  In 2015, there were 61 domestic flights with tarmac delays longer than three hours and 15 international flights with tarmac delays longer than four hours at U.S. airports.  All reported extended tarmac delays are investigated by the Department.

Chronically Delayed Flights - At the end of December, there were no regularly scheduled flight that were chronically delayed – more than 30 minutes late more than 50 percent of the time – for two consecutive months or more. This is the third month in a row in which there were no chronically delayed flights for two consecutive months or more. A list of flights that were chronically delayed for a single month is available from BTS.

Causes of Flight Delays - In December, the carriers filing on-time performance data reported total delays of 22.17 percent – 5.70 percent of their flights were delayed by aviation system delays, compared to 4.84 percent in November; 7.64 percent by late-arriving aircraft, compared to 5.18 percent in November; 6.13 percent by factors within the airline’s control, such as maintenance or crew problems, compared to 4.60 percent in November; 0.66 percent by extreme weather, compared to 0.42 percent in November; and 0.06 percent for security reasons, compared to 0.04 percent in November.  In addition, 1.68 percent of flights were canceled and 0.30 percent were diverted.

Weather - is a factor in both the extreme-weather category and the aviation-system category. This includes delays due to the re-routing of flights by DOT’s Federal Aviation Administration in consultation with the carriers involved.  Weather is also a factor in delays attributed to late-arriving aircraft, although airlines do not report specific causes in that category.

BTS uses the data collected from airlines to determine the percentage of late flights delayed by weather, which includes those reported in the categories of extreme weather, late-arriving aircraft, and National Aviation System delays.  In December 2015, 32.77 percent of late flights were delayed by weather, up slightly from 32.31 percent in December 2014 and from 30.45 percent in November 2015.

Detailed information on flight delays and their causes is available from BTS.

Mishandled Baggage - The U.S. carriers reporting mishandled baggage data posted a mishandled baggage rate of 4.04 reports per 1,000 passengers in December, down from December 2014’s rate of 4.26, but up from November 2015’s rate of 2.58.  For all of last year, the carriers posted a mishandled baggage rate of 3.24 per 1,000 passengers, down from 2014’s rate of 3.61.

Bumping - The report also includes reports of involuntary denied boarding, or bumping, for the fourth quarter of 2015 and calendar year 2015 from U.S. carriers who also report flight delay information.  These carriers posted a bumping rate of 0.72 per 10,000 passengers for the quarter, up from the 0.56 rate for the fourth quarter of 2014.  The carriers posted a bumping rate of 0.76 per 10,000 passengers last year, an improvement over the 0.92 rate posted in 2014.

Incidents Involving Animals - In December, carriers reported four incidents involving the death, injury, or loss of animals while traveling by air, down from the six reports filed in November 2015.  December’s incidents involved the deaths of three animals and injury to one other animal.  For all of last year, carriers reported 35 animal deaths, injuries to 25 other animals, and three lost animals, for a total of 63 incidents, up from the 45 total incident reports filed for calendar year 2014.

Complaints About Treatment of Disabled Passengers - The report also contains a tabulation of complaints filed with DOT in December against airlines regarding the treatment of passengers with disabilities.  The Department received a total of 81 disability-related complaints in December, up from the 67 complaints received in December 2014, but down from the 96 complaints received in November 2015. For all of last year, the Department received 939 disability complaints, up 19.8 percent from the total of 784 received in 2014.