Unionized pilots at Asiana Airlines launched an indefinite work-to-rule protest on Wednesday amid differences with the management over a wage hike.

At a kickoff ceremony, the union declared the start of the collective action at 10 a.m. involving legal means to delay takeoffs, such as pushing back the start of pre-flight briefings among pilots and cabin crew by over half an hour.

The union claimed that while the nation's second-largest commercial carrier enjoyed an operating profit of over one-point-two trillion won, or almost one billion U.S. dollars, over the past two years due largely to employees' hard work, the company refuses to meet their demand for a raise.

It accused management of placing priority on generating profit while neglecting flight safety, before announcing a possible strike should the company continue to come to the negotiating table without sincerity.

With around 77 percent of Asiana's one-thousand-411 pilots unionized, the airline has pledged flight adjustments and route changes to mitigate passenger inconvenience.

The union is demanding a ten-percent hike against the company’s offer of  a two-point-five-percent increase.