Delta Air Lines pilots begin voting Wednesday on a proposed labor contract that would increase their pay by nearly 14.5 percent in 2016 compared with today’s rates.

Some of Delta’s more than 12,000 pilots, however, are unhappy about other terms of the three-year agreement, including changes to profit sharing and work rules.

The period for Delta pilots to vote on the tentative labor agreement runs from June 24 through July 10.

Mike Donatelli, chairman of the Air Line Pilots Association at Delta, told pilots in a recorded message, “Our rates have suffered the trials of Delta’s highs and lows.” He said the tentative agreement represents “an opportunity to lock in a contract” that makes certain the future for pilots.

The union reached the agreement with the company six months before the pilots’ current contract expires, following Delta’s reporting of billions of dollars in profits. Donatelli told pilots that other carriers that waited longer are “mired in stalled negotiations. Imagine record profits, yet nothing to show for it.”

Tim Caplinger, a pilot who has been seeking to organize a new independent pilots union at Delta, said he sees the deal as a “concessionary contract.” He said some pilots are asking for 20 percent raises and no reduction in profit sharing.

“The money is there,” Caplinger said.