PITTSBURGH (AP) — Delta Air Lines ranks first in a long-running study that ranks U.S. airlines by how often flights arrive on time and other statistical measures.

Researchers who crunch the numbers also say that as a whole, U.S. airlines are getting better at handling baggage and overcrowded flights and are getting fewer complaints.

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Academics at Wichita State University and Embry-Riddle Aeronautical University have conducted their annual study for 29 years, using data collected by the U.S. Transportation Department. They released the results Monday.

They looked at 2018 rates of on-time arrivals, mishandled baggage, bumping passengers and consumer complaints.

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Delta is up from second place last year. JetBlue Airways is second, followed by Southwest Airlines and last year’s winner, Alaska Airlines.

Discount carrier Frontier Airlines ranks last, just behind American Airlines.

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