Sydney Airport is preparing for its busiest day in two years as travellers fly out for Easter holidays, with passengers stuck in queues as staff shortages strain systems.

Early on Wednesday traffic around the domestic airport was backed up for a kilometre, while queues outside the terminal snaked back for up to 100 metres.

Sydney Airport CEO Geoff Culbert has acknowledged passengers will be trapped in long queues as they wait to board flights.

“I want to start by apologising to them for any inconvenience,” he told Sydney radio 2GB on Wednesday.

“It’s another busy day,” he said.

The delays to processing passengers were primarily due to staff shortages.

“Everyone in the aviation industry has been rebuilding their business from the ground up,” Mr Culbert said, adding it was impossible to recruit enough staff and the airport’s security provider had 100 vacancies.

“But then you add on that the COVID issues – on any given day up to 20 per cent of staff can’t come to work due to COVID,” he said.

Security queues were moving well at T2 domestic terminal on Wednesday morning, while check-in wait times were peaking at about half an hour, a Sydney Airport spokesperson told AAP.

It’s expected that more than 80,000 domestic passengers will pass through the airport on Thursday as people get away for the Easter long weekend.

Mr Culbert said the airport would usually boost its resources to cater for increased holiday traffic but was struggling to find staff.

“We’re doing the best we can – we’re mobilising staff from all different areas of the airport … but the bottom line is when you’re operating at 60 per cent of staff capacity and you’re back at almost 100 per cent of passenger numbers – then there’s going to be a shortfall.”

Passengers are advised to arrive at least two hours before a domestic flight and three hours before an international flight.

Mr Culbert advised people to check-in online if possible and avoid bringing checked baggage if they could.

Other airports are preparing for increased traffic over the Easter weekend, with expectations it will be the busiest time of the last two years.

Adelaide Airport expects 25,000 people through its recently expanded terminal on Thursday and again on Friday.

Brisbane Airport expects more than 50,000 passengers on Thursday.