Talks between British Airways and the Transport and General Workers Union (T&G) over the firm's pension deficit could collapse, the union has warned.
BA and T&G are set to meet again for further pension talks
"It could be that we fail to agree with all the uncertainty that a talks breakdown means," the T&G said.
BA warned recently that its pension deficit was set to double to £2.1bn, and proposed raising the retirement age and cutting benefits to fund the gap.
After discussions on Thursday, both parties are set to meet next Wednesday.
"We have made it clear to BA in a series of meetings that the package of cuts is unacceptable," said Brendan Gold, national secretary for civil aviation at T&G.
BA has proposed raising the normal retirement age to 65.
The airline plans to keep its final salary pension scheme, with no increase in staff contribution rates, and will make a £500m one-off payment if unions agree to new arrangements.
"We will meet again next Wednesday but BA managers need to demonstrate that they have listened and are prepared to move," said Mr Gold.
Previously, BA's chief executive Willie Walsh has described the company's proposal as "a fair solution".