The aircraft is not one of Boeing’s 737 MAX 9 planes which have been in the spotlight after Alaska Airlines blowout.

Flight 1182 was headed to Toyama airport in Japan but headed back to the Sapporo-New Chitose airport after the crack was found on the outermost of four layers of windows surrounding the cockpit, a spokesperson for the airline said on Saturday.

There were no injuries reported among the 59 passengers and six crew, the airline added.

“The crack was not something that affected the flight’s control or pressurisation,” the ANA spokesperson said.

This is the second incident involving a Boeing aircraft in a week.

The ANA plane, also a 737 model aircraft, is however not one of Boeing’s 737 MAX 9 aeroplanes which have been in the spotlight since an Alaska Airlines flight suffered a blowout that left a gaping hole in the side of the fuselage last Saturday.

While the Alaska flight also landed safely with all 174 passengers and six crew members, flight data showed the plane climbed to 16,000 feet (4,876 metres) before returning to Portland International Airport.

Alaska Airlines has said it was grounding its fleet of 737-9 aircraft.

Planes ‘grounded’

On Friday, the US Federal Aviation Administration (FAA) said that all 737 MAX 9 planes would remain grounded until Boeing provides further data following the near-catastrophic Alaska Airlines incident.

“For the safety of American travellers the FAA will keep the Boeing 737-9 MAX grounded until extensive inspection and maintenance is conducted and data from inspections is reviewed,” the FAA said in a statement.

The regulator has also launched a safety probe into the incident, the first major in-flight safety issue on a Boeing plane since fatal 2018 and 2019 737 MAX crashes that led to a lengthy grounding of the aircraft.

“We are working to make sure nothing like this happens again,” FAA administrator Mike Whitaker said.

“Our only concern is the safety of American travellers and the Boeing 737-9 MAX will not return to the skies until we are entirely satisfied it is safe.”

In a statement on Friday, Boeing welcomed the FAA’s announcement and said the company would “cooperate fully and transparently”.

“We support all actions that strengthen quality and safety and we are taking actions across our production system.”

Boeing 737 Max jets have been grounded worldwide in the past. In October 2018 they were not let to fly for almost two years after a crash in Indonesia killed 189 people, and another in Ethiopia five months later, which killed 157 people.

The aircraft was cleared to fly again after Boeing revamped its automated flight-control system that had activated erroneously in both crashes.