DALLAS — Coming off another highly profitable year in 2016, U.S. airlines expect traffic this spring to increase 4% over last year, and they are adding seats to handle the crush.

The trade group Airlines for America forecast Monday that a record 145 million U.S. passengers will fly between March 1 and April 30.

The group’s chief economist says traffic will rise because airfares have been falling while economic indicators such as household wealth and job creation are rising.