(Adds details about engine issues)

By Alwyn Scott

NEW YORK, March 10 (Reuters) - Pratt & Whitney said on Thursday its new geared turbofan jetliner engine logged high reliability at its initial customer, Deutsche Lufthansa AG , a day after Qatar Airways raised concern about the engine's performance in hot climates.

Lufthansa took delivery of the first Airbus A320neo jet, equipped with the Pratt & Whitney's engines, in January. Launch customer Qatar Airways said on Wednesday the engines were not adequately tested and that it was seeking performance guarantees from Airbus and Pratt.

Bob Leduc, president of Pratt & Whitney, said at an investor conference held by parent United Technologies that faulty readings in the cockpit aren't related to engine issues and that a software fix was delivered last week to address that problem.

"We're 99 percent dispatch reliable at Lufthansa," Leduc said. "An engine that's not robust, an engine that's not durable, does not demonstrate 99 percent dispatch out of the box."

The company also introduced a hardware fix to the engines on its production line in late February to address the extra time required to start in certain heat conditions, United Technologies Chief Executive Greg Hayes said.

Engines with the hardware fix will be delivered in May or June, while those delivered earlier will be retrofitted, Hayes said.

A further software fix is planned for the fall of 2016, and after that the engine start time will be comparable to the V2500 engine made by International Aero Engines, a joint venture between Pratt, Japanese Aero Engine Corp and MTU Aero Engines, Hayes added.

Hayes noted that low-cost Indian airline IndiGo had taken delivery on Thursday of its first A320neo aircraft, which is equipped with Pratt's Geared Turbofan engine.

Leduc said Pratt is building up a buffer of engine parts to ensure the company can deliver 200 GTF engines this year, as planned.

"I don't have the level of buffer, though, that I'm comfortable with. But we're going to build it," he said. "I've got high, high confidence that we're going to deliver 200 Geared Turbofan engines this year." (Reporting by Alwyn Scott; Editing by Meredith Mazzilli and Alan Crosby)