Malaysia Airlines' workers' union called Thursday for the struggling carrier's top managers to step down, adding to pressure with the fate of Flight MH370 still unknown almost three months on.

The union will urge the government not to renew the contract of MAS chief executive Ahmad Jauhari Yahya, believed to be expiring in September, said the union's executive secretary Jabbarullah Kadir.

Two other senior managers should also resign to revive the loss-making state-controlled national carrier's fortunes, he added.

"Their business plan to turn around the airline hasn't worked. For us they totally failed to carry out their duty," Jabbarullah told AFP.

He said the union had rallied behind MAS over the jet that vanished flying from Kuala Lumpur to Beijing on March 8 carrying 239 people but that staff morale was "very low" over the carrier's poor financial performance.

The influential union represents about half of Malaysia Airlines' 19,500 worldwide employees and was instrumental in blocking a tie-up with rival budget carrier AirAsia three years ago.

Malaysia Airlines said earlier this month that MH370's disappearance had had a "dramatic impact" on earnings.

The carrier has struggled amid intense competition, losing $1.3 billion over the past three years before the impact of MH370 is taken into account.

For this year's first quarter the airline posted a net loss of 443 million ringgit ($137 million).

It was the fifth straight quarter loss and the worst since the fourth quarter of 2011 when it recorded a net loss of 1.28 billion ringgit.

No trace of MH370 has been found despite an extensive search in the southern Indian Ocean where it is believed to have come down.