The numbers are in: More than 35.1 million passengers flew into or out of Minneapolis-St. Paul International Airport in 2014. That represented a 3.7 percent increase over 2013, airport officials said.

And that is despite a 4.3 percent decrease in the number of planes coming and going.

"Airlines have been steadily right-sizing their aircraft fleets, eschewing the smaller regional jets for larger jets they are able to fill almost to capacity, unlike years ago when planes flew regularly with only about 65 percent of their seats filled," said Dennis Probst, executive vice president of the Metropolitan Airports Commission.

During the recession years of 2008 and 2009, passenger traffic had fallen nearly 5 percent, then slowly rebounded with modest gains of less than one-half of 1 percent to 1.4 percent a year through 2013. The big increase bodes favorably for MSP and the aviation industry, Probst said.

"The increase in passengers is indicative of a rebounding economy, where more individuals and businesses feel they can travel," Probst said.

Part of the surge can be attributed to Spirit Airlines, the discount airline that has rapidly gained travelers at MSP. Spirit served nearly 1 million passengers in 2014, a 359 percent increase over the previous year.

Just last month, the low-cost carrier moved its operations from Terminal 2 to the main terminal. With growing demand at Terminal 2, three new gates will be added, with construction beginning this spring. They are expected to be completed by 2016.

Delta, the dominant carrier at MSP, carried 17.18 million passengers in 2014, the most of any airline. US Airways had the second most passengers with 1.12 million, while American Airlines served 686,000 passengers, according to airport records.

Frontier Airlines will expand its offerings at MSP. Starting April 30, the Denver-based carrier will offer one nonstop flight to and from Philadelphia until the fall. The flight will depart Philadelphia at 2 p.m., arriving in Minneapolis at 3:50 p.m., and leave Minneapolis at 9:45 a.m., arriving in Philadelphia at 1:20 p.m.