A breakaway union of Virgin Atlantic pilots that called strikes during the Christmas and New Year's holidays extended the job action to the first eight weekends of 2019, according to an emailed statement.

The Professional Pilots Union sought help from the conciliation service ACAS to resolve the dispute, but Virgin Atlantic Airways Ltd. won't negotiate until it calls off the strikes, according to the union statement. A hearing is set for Thursday, two days before the first strike on Dec. 22 -- the weekend before Christmas.

The PPU said it called the action over its exclusion from talks on changes to pilot benefits.

Virgin Atlantic plans to challenge the strike action by seeking an injunction, the airline confirmed in response to email inquiries from Bloomberg News.

The PPU represents over a third of the 965 Virgin Atlantic pilot workforce, according to its statement. Virgin Atlantic said 16 percent of its pilots have voted to strike.