Crucial talks on tackling the huge pension fund deficit at British Airways are due to be held, with unions warning that negotiations have reached "high noon".
Officials from the Transport and General Workers Union and the GMB will meet company bosses in a bid to reach agreement over reducing the £2 billion black hole.
Ed Blissett, national officer for the GMB, said talks last week made no progress, adding: "BA failed to provide us with the details of the savings that GMB's proposals for the scheme would reap. We estimate the saving to be in the millions.
"The talks continue at high noon - appropriately enough as they will be the last as far as we are concerned."
The Transport and General Workers Union said the talks were in danger of "stalling".
National officer Brendan Gold said: "We have made it clear to BA in a series of meetings that the package of cuts is unacceptable. BA managers need to demonstrate that they have listened and are prepared to move. The way things are looking at the moment it could be that we fail to agree, with all the uncertainty that a talks breakdown means."
BA revealed earlier this month that its pensions deficit was set to more than double to over £2 billion despite a recovery in the stock market.
The airline proposed changes including raising the retirement age to 65 and capping pay rises to the rate of inflation. But union leaders described the measures as "unacceptable" and tabled counter-proposals aimed at heading off the threat of industrial action.
The airline has assured unions it would be keeping its final salary pension scheme, with no increase in staff contribution rates and no changes to pension benefits already earned.
Once the changes were accepted, BA said it would make a £500 million one-off payment to reduce the deficit.
