* Air Berlin to drop more routes to save money - sources
* First tranche of govt bridge loan received on Friday
* Bids for assets due on Sept. 15
* German businessman Skora drops out of running (Adds first tranche of bridge loan paid, Skora drops out of bidding)
FRANKFURT/BERLIN, Sept 8 (Reuters) - Insolvent German airline Air Berlin may drop more long-haul routes next week to cut costs as it races to find investors before it runs out of cash, people familiar with the matter said on Friday.
Air Berlin, Germany's second-largest airline, was forced to file for bankruptcy protection last month after shareholder Etihad Airways withdrew funding following years of losses.
Its planes are kept aloft thanks to a 150 million euro ($180.7 million) government bridge loan, which will last only until the middle of November at the latest. Air Berlin said it received the first instalment of the money on Friday.
The carrier had already announced plans to bring forward by a month to Oct. 1 the cancellation of its services from Berlin to Los Angeles and San Francisco, and from Duesseldorf to Boston.
This week it also said it was dropping flights from Berlin to New York and Miami, and from Duesseldorf to Orlando as of Sept. 25.
"The next step will be that further long-haul planes from Duesseldorf will be grounded," one person familiar with the industry told Reuters on Friday. Another person also said long-haul routes from Duesseldorf were to be dropped.
Air Berlin said talk of cancelling more routes was "speculation".
A handful of bidders is vying for Air Berlin's assets, with around 140 leased aircraft and valuable take-off and landing slots in Germany up for grabs.
German flagship carrier Lufthansa has government backing to take over large parts of the airline.
A source has told Reuters it could acquire as many as 90 of its planes, including 38 aircraft it was already leasing from the airline and its leisure unit Niki.
An industry source said Thomas Cook's Condor was also interested in Niki as well as further aircraft including crew, and would submit a binding offer next week.
Britain's easyJet is also expected to bid, with media reports saying it may be interested in up to 40 planes.
A few other investors have expressed interest in parts or all of Air Berlin, though they are seen as less likely to prevail.
Aviation investor Hans Rudolf Woehrl has said he expects to submit an offer for Air Berlin as a whole next week, with unnamed partners.
Former motor racing driver Niki Lauda told Reuters on Sunday he was working on a bid to buy back Air Berlin's Austrian unit Niki.
Utz Claassen, a former chief executive of German utility EnBW, is reportedly also interested in Air Berlin but has declined to confirm that.
German businessman Alexander Skora told Reuters on Friday he had decided against bidding for Air Berlin.
Bidders have until Sept. 15 to submit binding offers for the assets, with a decision possible as early as Sept. 21, three days before a German national election. ($1 0.8303 euros) (Reporting by Ilona Wissenbach and Klaus Lauer; Writing by Maria Sheahan; Editing by Edmund Blair)