Jetstar customers around the country are facing delays to their travel plans as ground crews and baggage handlers walk off the job to demand a pay increase and improved conditions.

Key points: Almost all major airports have experienced cancellations and delays

Almost all major airports have experienced cancellations and delays Workers are demanding a 4 per cent pay increase and better conditions to avoid risk of "serious injury"

Workers are demanding a 4 per cent pay increase and better conditions to avoid risk of "serious injury" Strikes took place this morning and will also take place again this evening

About 250 workers in Sydney, Brisbane, Melbourne, Avalon, Cairns and Adelaide were still striking on Friday afternoon.

Sydney staff are striking from 5:30pm to 7:30pm, while Melbourne strikes went from 4:00pm to 6:00pm.

Brisbane and Adelaide's will strike from 6:00pm to 8:00pm, having stopped work for two hours early this morning.

Passengers had been warned to expect disruptions, with flights cancelled at every striking airport.

Jetstar said some pilots would also stop work for four hours on Saturday and Sunday but all affected passengers have already been notified of cancelled flights.

In Sydney on Friday afternoon there were no long queues at check-in counters and most passengers were moving quickly.

However some passengers said they had been inconvenienced by the strike.

Grant Treloar was meant to be flying from the Gold Coast to Avalon but had been diverted to Sydney.

Grant Treloar's flight from the Gold Coast to Avalon was diverted to Sydney.

The last-minute change meant he would miss one day of the President's Cup golf in Melbourne.

"I'm a little bit peeved about that but otherwise it's not too bad," he said.

Anthony Beylouni's flight to the Gold Coast was delayed, causing his family to cancel some of their plans.

"It's been delayed a couple of hours and we've got activities booked. Now we just got to cancel them," he said.

"We're just praying … praying that we get there safely."

Michael Kaine, national secretary of the Transport Workers Union said it was "a source of regret that the travel plans of the public will be affected but that's at the feet of Jetstar.

"They need to come to the table, this can be resolved quickly with the will to do so."

In Brisbane, Transport Workers Union members had planned to march through the check-in area of the domestic terminal, but were stopped by Australian Federal Police officers from entering the building.

Transport Workers Union (TWU) secretary Peter Biagini said workers were left with no choice but to strike after Jetstar refused to meet their demands.

Workers fight against 'low pay, dangerous conditions'

Workers are fighting for a 4 per cent pay increase, more rest breaks, 12-hour breaks between shifts and a commitment to engaging Jetstar employees rather than untrained casual staff.

"These people are on less than $25 an hour and it's not a great deal to ask," Mr Biagini said.

"It doesn't only give them a decent pay but it also ensures that they're not fatigued and they're working safely."

Protesters from the Trade Workers Union in Melbourne support the industrial action today.

The union claims ground operations are dangerously understaffed with workers at risk of "serious injury" from being crushed by an aircraft.

It also says workers are being allocated to work on two aircrafts at one time.

"The airline has cut its staffing levels right back to the bone, meaning workers are constantly under pressure," TWU national secretary Michael Kaine said.

"Jetstar also allows broken equipment and machines to be kept in use despite the risk to workers and passengers. This is causing injury rates to go through the roof."

Jetstar disputed the claims the TWU has made about safety, saying it would never put their staff or passengers at risk.

"The TWU has a history of playing the safety card when it suits them, and this is another example of that," Jetstar said in a statement.

The budget airline said its resourcing practices were consistent with global aviation standards and in line with the practices of other airlines.

A SafeWork NSW spokesperson told the ABC that inspectors issued a safety notice to an airline operator at Sydney Airport on December 12.

"A notice was issued regarding safe work procedures relating to airline ground crews. SafeWork's investigation is ongoing," the spokesperson said.