"The restructuring process at Iberia still remains a slow work in progress, whilst rivals such as Easyjet and Ryanair continue to take advantage of prohibitive work practices still being suffered by former state airlines," said Keith Bowman, an equity analyst at Hargreaves Lansdown Stockbrokers.
"The airline is today testing investors' resolve," said Bowman, reflecting on the first quarter report from parent firm International Airlines Group, which also owns British Airways.
The report showed an loss of $820 million in the first quarter, compared with a loss of $167.6 million in the first quarter of 2012, the BBC reported Saturday.
Part of the loss includes a restructuring charge at Iberia of $404 million. The airline is also struggling due to the severe economic downturn in Spain, although revenue from passengers rose 3.9 percent in the first quarter.
"On the upside, management is clearly battling hard in Spain, with the long term aim of establishing a major hub to expected growth in Latin America," Bowman said.
"These results are encouraging with underlying revenue strength in strategic markets. However while the first step towards restructuring Iberia has been taken, there is more work to be done," said Chief Executive Officer Willie Walsh.