* Say plans "thorough review" of business plan
* Explores options to win back customers, manage costs
* Q1 earnings due after Malaysia stock market closes
(Adds MAS statement issued late Wednesday)
SINGAPORE, May 15 (Reuters) - Malaysia Airlines is going through a "thorough review" of its business plan to ensure it can sustain operations in the longer term, the loss-making company said in a statement late on Wednesday.
Addressing "intense speculation", the company also said it is exploring all avenues to win back customers and control costs.
"The plan will be shared with the relevant stakeholders at the appropriate time, when the necessary approval and endorsement have been obtained," it said.
Malaysian Airline System Bhd's (MAS) first-quarter earnings released on Thursday is set to show how badly the disappearance of MH370 on March 8 affected the carrier's finances.
The airline unveiled a business plan in late 2011 with the aim of turning a profit by 2013, by ending unprofitable routes and investing in new aircraft. However, MAS reported an annual loss for the past three years, prompting a change in direction.
Reuters reported last week that MAS is in talks with banks for a strategic overhaul, which may include the partial sale of its engineering unit and an upgrade of its ageing fleet.
Struggling to cope with high costs and nimbler regional and international rivals, MAS' quarterly performance has been made so uncertain by reduced traffic and potential costs linked to the jet's unexplained disappearance that analysts say they simply can't issue January-March estimates.
The carrier known as MAS reported a net loss of 343 million Malaysian ringgit ($106 million) for the last quarter of 2013, squeezed between AirAsia Bhd on short-haul routes, and Gulf carriers and AirAsia X in the medium and long-haul market. The first-quarter numbers are expected after the close of trading on the Malaysian stock exchange on Thursday.
Its worst quarter on record was in October-December 2011, when a series of one-off provisions related to jet deliveries and maintenance pushed it to a 1.28 billion ringgit net loss.
The airline said last month that passenger numbers dropped sharply after MH370's disappearance, its load factor - or percentage of seats sold - slipping to 74.1 percent, close to January 2013's record monthly low of 73.9 percent. Analysts expect the uncertainty over MH370 to continue to deter travelers from using the airline, 69 percent-owned by Malaysian state investor Khazanah.
"If there is new political will to restructure, MAS can be saved from itself, and our forecasts, target price, and perhaps even our recommendation may be raised," CIMB said in a report this week. But the brokerage, which has a 'reduce' rating on the shares, said the path forward remains risky.
Analysts have long urged change at the carrier. As part of a strategic overhaul of the company, MAS is looking to sell a stake in its profitable aircraft maintenance unit, sources told Reuters this week.
Regular customers like Ray Tan highlight the problem facing MAS. For the past two years, the Singapore-based technology executive flew MAS for business trips to Kuala Lumpur every fortnight.
Since flight MH370 disappeared, though, he has shunned the airline.
"If it's just the incident alone, I would think it's an isolated one, but right after it, there were a couple more breakdowns with the planes and that kind of really eroded confidence I had for MAS," said the 31-year-old, who won't even take the airline for leisure now.
Since last year, MAS has adopted a strategy of lowering fares to try and bolster traffic. Yet hampered by a strong trade union, it has also been unable to slash costs and improve productivity.
Analysts have argued that bringing in private investment and reducing the role of state investor Khazanah might promote change at the airline, improving competitiveness.
That prospect appears remote. Khazanah attempted to cut its stake in MAS in 2012, but the airline's main union successfully blocked a share swap deal with AirAsia that would have brought in a profitable airline with experience of competing aggressively.
"Their operating costs are still so high, they need to relook at the business model," said Kuala Lumpur-based Ang Kok Heng, chief investment officer at Phillip Capital. "Whatever restructuring they go through, they will have to overcome union opposition which is very difficult to do."
With no near-term improvement seen, investors including Khazanah may see the value of their holdings further eroded.
Since MH370 disappeared, MAS shares have slumped as much as 20 percent. Its market value has tumbled about 80 percent over the past five years, while the broader Malaysian market has risen about 80 percent. ($1 = 3.2385 Malaysian Ringgit)
(Additional reporting by Al-Zaquan Amer Hamzah in KUALA LUMPUR; Editing by Rachel Armstrong and Kenneth Maxwell)