Garuda Indonesia, the nation's flag carrier, may have to cancel some flights on Thursday as many of its 650 local pilots plan to launch a 24-hour strike over wage inequality, a spokesman for the pilots union said on Wednesday.

Garuda's chief operating officer Ari Sapari said not many pilots will go on strike and operations will run as usual.

The union is launching the strike as it says local pilots get paid less than half the wage of foreign pilots at Garuda, and because there had been no progress in discussions over the issue with the airline's management.

"They hired more foreign pilots with the same experience as us, but with higher wages," Stephanus Gerardus, the chairman of the Garuda pilots union, told Reuters. "We have asked 650 members of the union to go on strike tomorrow."

Garuda's Sapari said the union's demands were unclear and the management was waiting for the issue to develop before taking any action.

"It looks like not many pilots will go on strike, therefore I can assure you that operations will run as usual," Sapari told Reuters.

Garuda employs more than 800 pilots, including 43 foreign pilots, and has international flights across Asia, to the Middle East and to Europe.

Manotor Napitupulu, a Garuda pilot, said he will not take part in the strike on Thursday but predicted at least 50 percent of the 650 pilots will go on strike.

"We're supporting them but we will not follow the strike," Napitupulu told Reuters, speaking on behalf of some colleagues.

According to the union's Gerardus, a foreign first officer receives as much as US$7,200 a month, including housing benefits, while an Indonesian first officer receives less than 30 million rupiah a month.

This is the second Indonesian strike in July over wages after thousands of local workers at Freeport McMoRan Copper & Gold's Grasberg mine, one of the world's biggest copper and gold mines, went on strike for eight days, demanding hefty pay rises. The workers are still in pay talks.