US airlines canceled 3.7% of flights during the first four months of 2014, the highest rate in 20 years, according to the Bureau of Transportation Statistics. The figures continue to reflect US carriers’ response to the severe weather of winter 2014. Only similar first-four-month periods in 1996 (3.34% canceled), 1999 (3.49% canceled) and 2000 (3.31% canceled) can compare.

Cumulative on-time arrivals during the first four months also continued to reflect the troubles of the past winter season, with 74.07% of flights staying on schedule—the fourth-lowest rate for the January-April period in 20 years and the worst showing since 2008 (the lowest-ever at 72.6%).

Nonetheless, US carriers reported an on-time arrival rate of 79.64% in April, a 2.3 point improvement over April 2013, and the 10th highest rate for any April on-record, according to the BTS.

US passenger airlines canceled 1.1% of scheduled domestic flights in April, a 0.9 point drop from March’s rate, and a 0.7 point improvement on April 2013’s cancellation rate. 5,562 out of 483,499 scheduled flights were canceled in April.

US airlines reporting the lowest rate of canceled flights in April were Delta Air Lines, Frontier Airlines and Virgin America (all at 0.1%), Alaska Airlines (0.2%) and Hawaiian Airlines (0.3%). ExpressJet had the highest percentage of cancellations in April (3.4%), followed by Envoy Airlines (formerly American Eagle Airlines) at 3.2% and SkyWest Airlines (1.8%).

There were no US domestic flights with tarmac delays exceeding three hours in April. One international flight reported a tarmac delay exceeding four hours—a Virgin Atlantic flight on April 30 from London Gatwick Airport to Orlando International Airport, diverted to West Palm Beach International Airport. The aircraft was delayed on the tarmac for 267 minutes before continuing on to Orlando. Stormy weather in Orlando was the reported cause for the flight’s diversion.

In April, 7.5% of systemwide delays were due to late-arriving aircraft (i.e., the previous flight with the same aircraft arrived late, causing the present flight to depart late); 5.8% of the month’s flights were affected by national aviation system delays (i.e., non-extreme weather conditions, airport operations, heavy traffic volume, air traffic control, etc.); 5.3% of delays were caused by the air carrier (i.e., circumstances within the airline’s control, such as maintenance or crew problems); 0.4% of delays were caused by extreme weather; and delays occurring due to security reasons were only 0.02% of the month’s total.