Some flights from Perth Airport have left without luggage after part of the main runway was damaged when a Qantas plane took off on Sunday, dislodging a section of airstrip.

Perth Airport said 20 metres of pavement was damaged, and repair work was continuing.

The ABC understands some international flights have had to take off without luggage to meet weight restrictions on the shorter runway.

The incident took place about 12pm on Sunday, when a large slab of pavement on the main runway went flying in the air as a Qantas aircraft was making its departure.

Thirteen-year-old YouTuber Mitchell Booth, who recorded the incident, said he'd never seen anything like what occurred in his five years of plane spotting.

"When [the pavement] did lift up, it was quite high and it created a bit of dust … probably from when it smashed on the ground," he told ABC Radio Perth on Monday.

From his vantage point at the airport's viewing platform, Mitchell could see the damage was to a part of the runway that has recently been resurfaced.

"It's clearly caused by this new resurfacing, which is slightly concerning considering this is only the start of the resurfacing and it's already having issues," he said.

Mitchell said he believed the aircraft had its brakes set as it began moving along the runway.

"When they did increase thrust they still had their brakes set, which isn't too rare or anything but it's not what all aircraft do, they often do it when they are heavy," he said.

"This particular aircraft did rotate decently late down the runway, so it did need that power and due to the aircraft having so much thrust with it at the point, that probably contributed to that particular bit of concrete lifting up into the air."

Repairs continue

In a statement, Perth Airport said the incident damaged 20 metres of pavement that had recently been overlaid as part of planned repairs.

Work is underway to fix the impacted tarmac while the runway continues to operate.

"The Main Runway will continue to be used for departures while the recommended additional works are completed," a Perth Airport spokesperson said.

"These additional works are based on the advice of an external civil engineer, sought as part of an ongoing investigation to understand the cause of the pavement failure."

It is unclear how long the repairs will take.

The ABC understands some international flights have had to take off without luggage to meet weight restrictions on the shorter runway.

Government probe

WA Premier Roger Cook said the government would probe Perth Airport for an explanation of how this could happen.

"It's extraordinary that the tarmac would buckle in that way," he said.

"We're certainly looking for an explanation from Perth Airport. I understand that they have resurfaced that tarmac recently

"You shouldn't expect it to give way in such a fashion."

Mr Cook said the damage was concerning given the airport was "key economic infrastructure in WA".

"It's a very concerning piece of infrastructure failure," he said.

"We want Perth Airport to fix it as soon as possible."