Airline regulators will not be rushed into clearing grounded Boeing 737 Max 9 planes after a mid-air blowout, the US government has said.

The aircraft, which were suspended in the US following an incident on an Alaska Airlines flight “need to be 100% safe”, said Transportation Secretary Pete Buttigieg.

It is unclear when the planes will be allowed to fly again.

Boeing’s boss, Dave Calhoun, described the incident as a “quality escape”.

It means the incident was caused by some failure in quality control in the plane, which had been in service for just eight weeks before the blowout.

Mr Calhoun told CNBC that there were still questions that need to be answered about how the incident was allowed to happen. “What broke down in our gauntlet of inspections? What broke down in the original work that allowed for that escape to happen,” he said.

Earlier this week, Mr Calhoun admitted that Boeing was at fault after a section of the fuselage from a 737 Max 9 plane operated by Alaska Airlines blew-out within minutes of take-off.

No-one was injured when the panel – or door plug – broke away from the Alaska Airlines flight from Portland, Oregon, forcing the plane to make an emergency landing.

The US Federal Aviation Administration (FAA) grounded 171 Boeing jets on Saturday that were installed with the same door plug.