The biggest traffic gains were on flights within the U.S. and to Latin America. Traffic to Europe and Asia rose only slightly.
Delta reported the increase in passenger revenue for each seat flown one mile. That's a closely watched number in the airline industry, and it rises when airlines fill more seats or sell tickets at higher average prices. The figure rose just 1 percent in March.
Passengers flew 16.57 billion miles on Delta last month, up 6.6 percent from April 2013. Including Delta Connection regional flights, the company increased passenger-carrying capacity by 3 percent.
Since traffic rose faster than capacity, the average flight was more full — 84.7 percent, up from 81.8 percent a year earlier.
Shares of Atlanta-based Delta fell 2 cents to $37.10 in midday trading. They began the day up 35 percent this year, as airline stocks have rallied on stronger earnings after recent mergers.
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