MANCHESTER — Overall passenger traffic at Manchester Boston-Regional Airport fell 7.5 percent from January through April compared to the first four months of 2011.

The year-over-year decline for the month of April was even sharper at 15.2 percent.

For the first four months of the year, 760,105 passengers arrived or departed versus 821,733 for the same period a year ago.

Loss of four flights a day on Southwest between Manchester and Philadelphia beginning in January accounts for most of the decline, Deputy Airport Director J. Brian O’Neill said.

“Those four flights were operated in 137-seat aircraft, and I think the decrease in passenger activity is a direct result of not having those four flights in 2012 but having those four Philadelphia flights in 2011,” he said.

O’Neill said Southwest also cut Philadelphia service from Boston and Providence on Jan. 7, 2012.

“After several years of passenger declines, we are hopeful that we are now establishing a new baseline and as the economy improves and the price of oil stabilizes, we hope that we’ll turn the corner and start to see slow, steady growth again,” he said.

“There are so many factors in the airline industry that are unfortunately outside of the airport’s control,” O’Neill said.

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