Thousands of Malaysia Airlines workers are protesting its proposed alliance with budget rival AirAsia, warning the flag carrier would lose in the long run if it pulls out of the profitable low-cost sector.

In a surprising move last month, AirAsia and Malaysia Airlines inked a proposed share swap agreement to end their long rivalry and boost business. Under the deal, Malaysia Airlines will focus on the premium market and cede low-cost routes to AirAsia.

Malaysia Airlines Employees Union, representing 15,000 workers, says the deal benefits only AirAsia. The union warned Thursday it would stage a picket if the deal goes through.

Malaysia Airlines officials declined to comment.