Flight capacity has been restored at Sydney Airport after dozens of planes were delayed, some by more than an hour.

According to FlightRadar24, the delays started early on Friday and continued to get longer throughout the day.

WATCH THE VIDEO ABOVE: Sydney Airport chaos as air traffic control crisis deepens

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Normal operations have since resumed at the airport, but thousands of passengers have been left scrambling to rearrange travel plans as a result of the lengthy delays.

Qantas reported more than 50 flights were delayed by up to 90 minutes while four flights were cancelled.

Virgin Australia had 20 flights delayed, with two flights to Melbourne being cancelled, while 25 Jetstar flights were delayed.

Meanwhile, international carriers have had flights to tourist destinations such as Hong Kong and Seoul delayed by about an hour, according to FlightRadar24.

One passenger on board a flight to Cairns at 6.10am told 7NEWS the plane taxied for about 30 minutes before being brought back to the gate.

“I was wondering what was going on because we hadn’t taken off yet,” she said.

“Then we got an announcement saying there’s something wrong with the radar and also the backup radar wasn’t working as well.”

The plane then returned to the gate for technicians to work on the aircraft and took off about 90 minutes later.

Another passenger told 7NEWS he was set to depart on a flight to Hong Kong at 10.10am but was instead hit by a “one-and-a-half hour delay caused by air traffic control”.

“I can imagine that if you’re a frequent traveller, these sorts of delays trying to get to your destination are just ridiculous,” he said.

Airservices Australia addresses delays, says flight capacity restored

Airservices Australia told 7NEWS.com.au it had “enacted Air Traffic Flow Management (ATFM) measures at Sydney Airport due to operational restrictions to safely manage projected airborne and departure demands”.

“Airservices acknowledges the ATFM measures, which have now been removed, caused disruptions to airline scheduling, however capacity has now been restored and no further significant delays are anticipated.”

The government-owned corporation also acknowledged “recent media reporting and commentary about the performance of our air traffic controllers”.

“Airservices air traffic controllers are incredibly proud and dedicated to performing what is a demanding, safety-critical role,” it said.

“We take their wellbeing and psychosocial safety seriously and ask that commentary on operational performance recognises the professionalism and commitment of the controllers working every day to keep the travelling public safe.”