Swiss International Air Lines has returned to service the first of 29 Airbus A220s it grounded on Tuesday to conduct immediate inspections of their Pratt & Whitney PW1500G turbofans after the pilots of a London Heathrow-Geneva flight had to shut down one of the aircraft’s two engines in flight. In a written statement, the airline added that it expected a resumption of its schedule "in a largely regular manner" on Thursday. Tuesday's grounding forced the cancellation of some 100 flights and affected some 10,000 passengers.

The inflight shutdown of the PW1500G was the third Swiss has experienced within four months. An A220-100 operating a Geneva-London Heathrow flight on July 25 suffered an inflight shutdown as it approached its FL350 cruise altitude. The aircraft diverted to Paris Charles de Gaulle Airport. The airline’s second PW1500G inflight shutdown occurred on September 16 as the aircraft—also operating a Geneva-Heathrow flight—neared its cruise altitude, though in that incident the aircraft did not divert.

Both previous incidents involved the failure of the engine’s first rotating low-pressure compressor (LPC) stage. Following the two incidents the FAA issued an airworthiness directive (AD) on September 25 requiring repetitive inspections, beginning within 50 flight cycles, of the LPC Stage 1 rotors and inlet guide vanes in all in-service PW1500G and PW1900G engines with less than 300 flight cycles since new.

However, neither Swiss nor Pratt & Whitney has confirmed yet whether the latest A220 PW1500G inflight shutdown involved the failure of any of the engine’s LPC stages. Neither have they confirmed whether the engine in question had accumulated less than 300 flight cycles.

The aircraft involved in Tuesday’s incident, which again saw it diverting to Paris Charles de Gaulle following the shutdown, operated as flight LX359, according to Swiss. The incident occurred at 8:55 a.m. Central European Time (CET). Swiss told AIN that the A220 involved in today’s incident is an A220-300 registered HB-JCC. According to Airfleets.net, HB-JCC is a two-year-old aircraft that first flew on Aug. 2, 2017, and bears the manufacturer’s serial number 55012. Swiss operates 20 A220-300s and nine A220-100s.

A media statement issued by Swiss following today’s incident confirmed the airline had grounded its entire A220 fleet as of 3:10 p.m. CET to inspect their PW1500G engines. “Only following a faultless inspection will these aircraft be returned to regular flight duties,” said the statement. “This will put substantial restrictions on Swiss’s flight operations, as numerous flights will have to be canceled...Swiss takes these incidents very seriously, and is in close dialogue with the relevant authorities, with Airbus Canada and with the engines’ manufacturer (Pratt & Whitney).”

Pratt & Whitney issued its own statement following today’s Swiss A220 inflight shutdown. “Pratt & Whitney and our airframe OEMs, working in coordination with the regulatory authorities, has recommended additional inspections of the low-pressure compressor for PW1500G and PW1900G engines to keep the fleet operational,” the statement said. “This recommendation is related to the events involving recent PW1500G engines which are part of investigations being led by the U.S. National Transportation Safety Board (NTSB).”

P&W hasn’t yet confirmed if its statement today means that it is now recommending more frequent repetitive inspections of PW1500G and PW1900G LPC stages beyond those already mandated by the FAA’s September 25 AD. The engine OEM also hasn’t yet confirmed whether or not it now recommends that inspections begin immediately rather than within 50 flight cycles.

For its part, Airbus vowed to do whatever it can to minimize the disruption to Swiss’s operation. “Airbus is aware of the incident that happened earlier today, October 15, with a Swiss aircraft,” it said in a statement. “We sincerely regret this impediment for our customer and its passengers. Together with the engine manufacturer we are supporting our customer to minimize disruption to their operations. We will support the investigation in line with ICAO Annex 13 standards.”