STOCKHOLM (Reuters) - Ailing Scandinavian airline SAS and striking pilot unions will resume negotiations on Monday, public broadcaster NRK said, after failing to reach new collective agreements over the weekend.

Most SAS pilots in Sweden, Denmark and Norway walked out on July 4 after talks over conditions related to the carrier's rescue plan collapsed. The parties returned to the negotiating table in the Swedish capital last Wednesday.

"We are now going home after 37 hours to get some sleep," Henrik Thyregod, head of the Danish pilots' union, said as he left the Stockholm venue where negotiations are held, NRK reported.

Norwegian pilot union representative Roger Klokset had said earlier on Sunday that the parties may have come closer to a deal overnight.

"Maybe. But I don't know whether there will be an agreement yet," he said.

SAS, the main owners of which are Sweden and Denmark, had been struggling to compete with low-cost competition for years before the pandemic slammed the industry. It needs to attract new investors and secure bridge financing, saying that it must first slash costs to achieve those objectives.

Pilots employed in the 75-year-old carrier's SAS Scandinavia subsidiary last week said they would agree to limited wage cuts and less favourable terms, but SAS said the concessions offered were not enough for it to carry out a rescue plan announced in February.

Unions also demand that pilots axed during the pandemic are rehired at SAS Scandinavia rather than having to compete with external applicants for jobs on less attractive terms at recently created SAS Link and Ireland-based SAS Connect.

On Saturday a mediator said the parties had made progress, but significant issues had yet to be resolved.

The airline said on Thursday that the strike had caused 2,550 flight cancellations, affecting 270,000 passengers and costing it between $94 million and $123 million. The Swedish government has said it will provide no more cash.

For Sunday, 164 SAS flights, or 62% of those scheduled, were cancelled, according to flight-tracking platform FlightAware. Pilots at SAS Link and SAS Connect are not on strike.

(Reporting by Helena Soderpalm, Anna Ringstrom and Johan Ahlander,; Editing by David Goodman and Frank Jack Daniel)