Long Beach Airport passenger traffic surged 25 percent in June and 47 percent for the first half of the year, airport officials announced Thursday.

About 313,000 passengers boarded or departed planes at the municipal airport in June, up 25 percent from 2016 levels. About 1.85 million passengers went through the airport for the first half of the year, up 47 percent from the first six months of last year.

The main reason for the increases: more available seats on more flights. The number of available seats shot up 61 percent for the first half of the year to 1.18 million.

Long Beach officials last year acted to allow nine more daily flights from the airport, bringing the total to 50. Southwest Airlines Co. received four of those daily flights, JetBlue Airways Corp. three and Delta Air Lines Inc. two. The airlines immediately put those new flight allotments to use.

Southwest and JetBlue received one more daily flight each in March when American Airlines Inc. gave up two of its five daily flights. Beginning this month, Southwest has taken over both of these flights.

While passenger traffic has soared, air cargo tonnage has slipped. In June, 2,018 tons of cargo went through Long Beach Airport, down 11 percent from a year earlier. For the first half of the year, 11,344 tons of cargo went through the airport, down 8 percent from the first six months of last year.

Public policy and energy reporter Howard Fine can be reached at [email protected]. Follow him on Twitter @howardafine.