* Pilots to strike on short- and long-haul on Wed & Thu
* Frankfurt court allows strike, Lufthansa appeal rejected
* Lufthansa cancels 876 flights on Wed alone
* Walkout is 14th in ongoing labour dispute (Recasts with continuation of strike on Thursday)
By Maria Sheahan and Peter Maushagen
FRANKFURT, Nov 22 (Reuters) - Lufthansa has cancelled hundreds of flights scheduled for Wednesday and will also be forced to ground planes on Thursday as its pilots plan a 48-hour walkout, the latest threat of disruption to its operations in a long-running pay dispute.
The pilot union said in a statement that all of Lufthansa's short and long-haul flights out of Germany will be affected by the continued industrial action, planned to run until 2259 GMT on Thursday.
The strike is the 14th to hit the airline in its row with the Vereinigung Cockpit (VC) union and the airline said it has cancelled 876 of roughly 3,000 flights scheduled for Wednesday, affecting about 100,000 passengers.
Lufthansa was seeking to prevent the strike going ahead late on Tuesday after a Frankfurt labour court earlier rejected its application for an injunction.
But a judge at the Hesse state labour court rejected the company's appeal and said the strike may go ahead, adding that the labour dispute was too complex to be properly dealt with in the form of an expedited injunction.
The pilot union announced Thursday's ongoing strikes immediately after the verdict.
The planned Wednesday strike will run from midnight and affect short-haul and long-haul flights departing from German airports.
Flights by Lufthansa's other airlines including Germanwings, Eurowings, Austrian Airlines, SWISS and Brussels Airlines, are not affected by the pilots' strike, Lufthansa said.
Austrian and SWISS are checking whether they can use larger aircraft to increase the number of passengers they can take. For example, the group plans to use a widebody Boeing 777 on the Vienna-Frankfurt route, it said.
However, budget airline Eurowings cancelled around 60 flights on Tuesday due to a strike by some cabin crew in a separate pay dispute between management and the Verdi labour union.
Pay talks between Lufthansa and VC broke down this month, and the pilots have rejected calls by Lufthansa for the dispute to be taken to a mediator.
The union is calling for an average increase of 3.7 percent in pay for 5,400 pilots in Germany over a five-year period dating back to 2012.
However, Lufthansa, which is trying to cut costs to cope with increased competition from low-cost carriers and leaner Gulf rivals, has offered a 2.5 percent increase over the six years until 2019. (Writing by Tina Bellon; Editing by Jonathan Oatis and Sandra Maler)