(Adds Delta and union comments, timeline, background)
Sept 30 (Reuters) - Delta Air Lines Inc and its pilots union have reached an agreement in principle for a new contract that has been more than a year in the making, the parties said on Friday.
The deal, reached with the help of U.S. federal mediators, requires the approval of union leaders before it can become a so-called "tentative agreement," which pilots can vote to ratify or reject. About 65 percent of voting pilots turned down the last tentative agreement in July 2015.
Delta did not immediately return a request for comment on the terms of the agreement. But in a statement, it called it an "industry-leading package of pay, benefits and work rules."
The last tentative agreement offered an 8 percent pay hike upon signing. However, opponents said the gains were slight considering Delta's growing profits and that higher wages came at the expense of more-lucrative profit-sharing. Changes in sick leave and other work rules also offset the gains, the critics said.
Following the rejection, the leader of Delta's unit of the Air Line Pilots Association, International resigned. The parties did not come to terms by the old contract's target date for revision of Dec. 31, 2015.
In a statement, the union's Chairman John Malone said the Friday's agreement "achieves the goal of advancing the profession... (and) recognizes and rewards the Delta pilot group for the daily contributions we make to Delta's financial success."
The union said it has seven days to review the agreement before deciding whether to put it up for a pilot-wide vote. (Reporting By Jeffrey Dastin in New York; Editing by Chizu Nomiyama and Dan Grebler)