British Airways said it reached a preliminary agreement with labor groups representing some ground-based employees as it seeks to cut costs and ride out a deep slowdown triggered by the coronavirus pandemic.

BA has signed outline deals with the Unite and GMB unions that cover engineers and customer-facing staff at its London Heathrow hub, Chief Executive Officer Alex Cruz said in an internal memo seen by Bloomberg News.

The airline said it has yet to reach an accord with “below the wing” ground workers employed in activities including baggage handling and refueling.

The GMB said BA’s styling of the situation as a breakthrough was misleading, and that the IAG SA unit had used the threat of firing and rehiring workers to transform a reasonable deal into one resulting in “glorified zero hours contracts” involving additional pay cuts and a lay-off clause. That said, an agreement in principle has been signed that will now be subject to a member ballot, the GMB said by email.

British Airways has warned that as many as 12,000 posts may need to go as a result of the Covid-19 crisis and said last week that 6,000 employees had chosen voluntary redundancy. The carrier’s pilots voted in July to accept a deal that would reduce the number of job losses in return for pay cuts, but negotiations with other unions including those that represent cabin crew have proved more intractable.

Cruz said that consultations continue across all other parts of the airline.