TORONTO (Reuters) - Bombardier (>> Bombardier, Inc.) will delay the first test flight of its Learjet 85 business jet after discovering a systems problem that requires a software update, the Canadian company said on Wednesday in the latest setback for its aircraft development program.

A company spokeswoman declined to provide a new timetable for the Learjet's maiden flight, and would not offer details on the nature or seriousness of the problem.

After a weather-related delay of the first flight last week, Bombardier identified a "systems issue", said Annie Cossette, a spokeswoman for Bombardier's business aircraft division.

"Right now, our teams are focused on addressing the matter to ensure that the aircraft can fly safely," Cossette said.

"The (software) update is part of the ongoing systems review that we conduct as part of first flight preparations. I can't provide any more information as to what system."

The delay is the latest to plague Bombardier's aircraft development program. The company has been struggling to get its costly new CSeries commercial aircraft into service. That plane now is not expected to take commercial passengers until sometime in the second half of 2015, at least 1-1/2 years behind schedule.

The CSeries - meant to fill a potentially lucrative niche and to compete with the smaller jetliners made by industry giants Boeing Co (>> The Boeing Company) and Airbus Group (>> AIRBUS GROUP) - was originally set to be in service around the end of 2013.

The Learjet 85, Bombardier's largest Learjet, was originally set to enter service in late 2013, but early last year the company pushed the date to the summer of 2014.

Montreal-based Bombardier has since said it will not set an entry-into-service schedule for the Learjet 85 until the plane has flown for up to two months.

The Learjet 85 was ready to take flight from Wichita, Kansas, last Thursday morning, but weather conditions were not optimal. At the time, Chief Executive Pierre Beaudoin told investors that the first flight was still imminent.

(Editing by Franklin Paul; and Peter Galloway)

By Solarina Ho

Stocks treated in this article : AIRBUS GROUP, The Boeing Company, Bombardier, Inc.