It appears that the inclement weather that sparked cancellations and delays for North American carriers at the end of December had a negative effect on their overall on-time monthly performance.
Average North American airline on-time performance in December plunged more than 10 percentage points to 65.8 percent from 76.4 percent in November, according to Cirium's monthly report. Every included carrier's performance dropped. Delta Air Lines remained in the top spot at 79.5 percent, while American Airlines jumped from fifth to second at 73.5 percent.
Southwest Airlines, which had more troubles than the other carriers at the end of December, dropped to 69.4 percent from 80.2 percent the month prior, but remained above the industry average.
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For December global on-time performance, Delta was fifth and American was 10th. United Airlines (72.6 percent) dropped off the list after it had been fifth for the prior two months.
The report also showed year-over-year growth of 7.18 percent in the number of flights completed.
A flight is considered on time if the aircraft arrives at the gate within 15 minutes of the scheduled arrival time.
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