The government says there were four planes stuck on the tarmac for more than three hours in April. U.S. airlines were also worse overall at getting passengers to their destinations on time.
Three of the flights held on the ground for more than three hours in April were operated by Delta; the other was a United plane. Three of those flights were later cancelled.
The month of April tends to be heavy with thunderstorms in many parts of the country.
Bad weather was the main culprit in slowing down planes overall during the month. The Transportation Department says the country's 16 largest airlines reported had an on-time rate of 75.5 percent, down significantly from a rate of 85.5 percent a year ago and 79.2 percent in March.
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