* Lufthansa eyes 12 of the 17 long-haul planes - source
* Lufthansa most interested in routes to U.S. - source
* Ryanair says most interested in Air Berlin routes
* Bids for Air Berlin assets due by mid-September (Recasts with source on Lufthansa, adds Ryanair comment, details)
FRANKFURT, Aug 29 (Reuters) - German airline Lufthansa aims to take on around a dozen of Air Berlin's 17 long-haul aircraft in a carve-up of the insolvent carrier, a person familiar with the matter told Reuters on Tuesday.
Air Berlin, Germany's second-largest airline, filed for bankruptcy protection this month after shareholder Etihad Airways withdrew funding following years of losses.
At least half a dozen bidders for Air Berlin's assets are now racing to submit offers by a mid-September deadline, with around 140 leased aircraft and valuable take-off and landing slots in Germany up for grabs, among other.
Lufthansa is especially interested in Air Berlin's routes to U.S. cities including New York and Washington D.C., the source said on Tuesday.
"The plan foresees stationing two of the planes in Berlin and up to 10 in Duesseldorf," the person said.
Earlier this month, a source had said Lufthansa could take on as many as 90 of Air Berlin's roughly 140 leased planes, including 38 aircraft it is already leasing from Air Berlin and its leisure airline Niki.
Thomas Cook's Condor, easyJet and Ryanair are also among airlines interested in the carrier's business or parts of it, sources familiar with the negotiations have said.
Ryanair's marketing chief Kenny Jacobs said on Tuesday that the Irish low-cost carrier was primarily interested in Air Berlin's routes.
Chief Executive Michael O'Leary has told Reuters he would also be interested in a bid for Air Berlin as a whole, but he has complained Ryanair hadn't been invited to the process, which he sees as heavily favoring Lufthansa.
German aviation investor Hans Rudolf Woehrl is also due to hold talks over Air Berlin's assets on Wednesday, and former motor racing driver Niki Lauda has indicated his interested in buying back Niki, the Austrian airline he once owned.
According to Air Berlin, bidders have until Sept. 15 to submit their offers. (Reporting by Ilona Wissenbach and Peter Maushagen; Writing by Maria Sheahan; Editing by Tom Sims/Keith Weir)