MONTREAL (Reuters) - A software update for the GTF engine on Airbus' smallest jet, the A220, is expected in the spring, pending regulatory approval, a top executive at United Technologies Corp's UTX.N Pratt & Whitney aircraft engine division said on Wednesday.

FILE PHOTO: The logo of Dow Jones Industrial Average stock market index listed company United Technologies and their subsidiary Pratt & Whitney is pictured in San Diego, California April 21, 2016. REUTERS/Mike Blake

Checks were ordered on the GTF on the Airbus AIR.PE plane last year following engine failures on aircraft operated by Lufthansa LHAG.DE subsidiary Swiss International Air Lines AG. [SWIN.UL]

Reuters reported last year that a U.S.-led investigation into a series of engine failures on the A220 was studying whether a software change allowed unexpected vibrations that tore parts and forced three emergency landings.

“We’re going to have a software drop that comes out later this year that will automate everything and enable us to reduce or eliminate all the inspections that we’re currently having to perform, but that again is pending regulatory approval,” Graham Webb, vice president of Pratt & Whitney commercial engine programs, told Reuters.

“We’re trying to bring it into April, so safe to say in the spring,” he added.

Neither the A220 plane nor the engine have been grounded but Airbus and Pratt & Whitney have told pilots not to push engines above 95% of their maximum thrust when flying above 29,000 feet - a demanding configuration currently required only by Swiss.

"It's a very strange and very complex issue that occurs at high altitude and high speeds," added Webb, who spoke on the sidelines of an Air Canada AC.TO event in Montreal.

Airbus Chief Commercial Officer Christian Scherer praised Pratt & Whitney for its quick moves to address problems with its GTF engines on both the A220 and A320 NEO family planes.

“That said, we are never satisfied,” Scherer told Reuters on the sidelines of the same event. “We always want it quicker. We always want it better and we will continue to keep that pressure on.”

Nobody was hurt in the three incidents, which all took place on the 750 km (470 miles) route between London and Geneva.

On modern aircraft, engine settings are controlled by engine manufacturer software that interprets pilot commands and tells the engines what to do. The Swiss problems first arose following a recent update of the software, Reuters previously reported.

(This story corrects headline, adding words “software update” and removing “approval for” to reflect that the engine does not need approval.)