Niki's administrator began urgent talks on Thursday to find a buyer for the insolvent Austrian carrier after a deal with Lufthansa fell through and with valuable runway slots at risk of being lost.

German flagship carrier Lufthansa scrapped plans to buy Niki on Wednesday due to competition concerns, grounding the airline's fleet and stranding thousands of passengers in what its managing director said was a "national disaster for Austria".

So far, former motor racing driver and Niki's founder Niki Lauda and tourism group Thomas Cook TCG. have expressed an interest in taking over Niki.

SLOTS

A spokesman for Niki's administrator said the carrier would lose its runway slots in a few days, one of the most attractive assets for possible buyers.

In Europe, when airlines go bust, their take-off and landing slots are usually returned to a pool and redistributed unless a buyer is found for the airline business.

Niki planes have been granted around 1,800 slots, or around 1.6 percent of the available slots in Austria, for the winter season which ends March 23, according to the coordinating authority Slots Austria.

For the following summer season, which ends in October 2018, they have 1,700 slots.

After filing for insolvency, Niki to get special permission by the transport ministry within days to keep the slots, Gallistl said.

"There is agreement on an expert level that the Niki slots should be extended," said Wolfgang Gallistl, Slots Austria's managing director, adding: "Then the nearly 1,000 staff have a perspective."

The Transport Ministry had no immediate comment on the issue. It said, though, that it was considering providing a bridge loan to Niki and that it had "very good" discussions with the finance minister about it.

POTENTIAL BUYERS

Niki is owned by Air Berlin, which itself collapsed earlier this year. Air Berlin's administrator Frank Kebekus said he hoped to agree a deal for Niki by the end of the year.

"If we had that, then we can certainly take another week or two in January to finalize it," he told rbb-Inforadio.

Three to four parties are interested in taking over Niki, Wolfgang Katzian of Austrian union GPA told broadcaster ORF earlier on Thursday, without naming them.

Lauda, who offered around 100 million euros jointly with Thomas Cook's airline Condor for Niki plus 17 aircraft before Air Berlin was carved up, said he was still interested but would try to take over Niki without a partner.

Thomas Cook said it was considering either taking over Niki as a whole or buying parts of it.

Irish low cost carrier Ryanair wants to review Niki's slots, and said there may not be enough for it to be interested.

British Airways parent IAG has dropped out of the bidding.

PASSENGERS AND STAFF WAIT AND HOPE

Austria's Transport Ministry estimated that about 5,000 Niki passengers could be stranded in the next two weeks. Many of them will be able to fly home on other airlines, but the ministry has started talks to charter some planes.

Management addressed Niki's workers at a town hall meeting at Vienna airport on Thursday, which one staff member said ended in a heated argument over their future.

"Let's wait and see whether we still get our salary... Questions on that were not answered," Niki technician Sebastian van Ven, who attended the meeting after working the night shift, told Reuters.

He said salaries for November were due to be paid on December 28.

Lufthansa subsidiaries Eurowings and Austrian Airlines began advertising for crews, saying they would offer shorter recruitment processes than normal for any former Air Berlin or Niki staff.

German industry body BDL said German airlines would help return Niki passengers home by offering them available seats on their flights at "rescue fares". Lufthansa's Eurowings and tourism group TUI are offering such fares.