Thick fog rolled in across Sydney as the sun rose and saw visibility reduced and flights delayed.

The first Qantas flight out of Tamworth bound for Sydney landed earlier than expected, but the 10.40am service to the big smoke was delayed by 44 minutes.

Pilots managed to make up time with Tamworth passengers landing in Sydney at 12.10pm.

The 1.35pm service to Sydney was delayed until 2.15pm, Qantas advised.

Qantas said in a statement on social media that several flights had been impacted.

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"Due to the fog in Sydney this morning, a number of flights have been delayed across the network," the spokesperson said.

Pilots managed to make up time in the air for the mid-morning flight from Sydney to Tamworth. It took off 14 minutes late before it arrived in the country music capital just after its 10.15am standard arrival time.

The midday service was delayed by more than one hour and 15 minutes, and is due to land in Tamworth at 2pm.

A spokesperson for Sydney Airport said the foggy weather, along with a technical issue to do with security, had delayed passengers and flights.

Hundreds of people could be seen on social media waiting in line on arrival to the airport.

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