Delta Air Lines pilots begin voting Thursday on a proposed new labor contract that would give them pay raises of 30.2 percent over four years.

If they vote in favor of the deal, Delta's 13,000 pilots would get immediate pay raises of 18 percent when the contract takes effect, retroactive to Jan. 1, 2016.

Then, on top of that, they would get a 3 percent raise in 2017, followed by another 3 percent raise in 2018 and a 4 percent raise in 2019.

The Air Line Pilots Association union at Delta has been pushing for raises to make up for pay cuts of as much as 50 percent that pilots sustained during the company's financial struggles and bankruptcy a decade ago.

While in contract negotiations  earlier this year, union members had been picketing in front of Delta's Atlanta headquarters, at airports and at the company's annual shareholder meeting.

The pilots union leadership voted 15-4 to recommend the tentative agreement for approval. The pilots will cast ballots on the deal via online voting through Dec. 1.

Pilots are the only major unionized employee group at Delta.