A hazardous materials incident on a plane at Melbourne Airport is over but it is not yet known if the suspicious packages posed a risk.

Packages containing white powder found by cleaners on an international flight that was on the tarmac of the airport have been removed by firefighters in hazmat gear.

The Metropolitan Fire Brigade says the incident is “contained” and a statement is expected from the Australian Federal Police.

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Meanwhile, travellers in Sydney were worst hit by strikes at Australia’s major airports, with long queues building while customs officials protested proposed cuts to their pay and conditions.

Emergency services on the tarmac. Photo: Twitter

More than 200 staff marched outside the airport on Wednesday morning carrying placards and chanting to oppose the Abbott government’s workplace bargaining policy.

Meanwhile, queues for travellers entering the country stretched more than 100 metres at customs check points, a customs union spokesman told AAP.

Passengers waiting to check in for their flights were frustrated as lines stretched out.

“I think it’s ridiculous, school holidays every time, everyone’s got to strike,” one female passenger told the Seven Network.

In Melbourne, an airport spokesman said staff had been prepared for a busy day with the strike and school holiday traffic.

The Community and Public Sector Union called the two-hour strike from 9am at airports in Sydney, Melbourne, Brisbane, Gold Coast, Adelaide, Perth and Darwin as well as seaports.

“We regret any inconvenience to the public as our message is for the government who is trying to strip rights and pay from workers,” CPSU spokesman Chris Taylor said.

Mr Taylor said under the government’s deal about $8000 will be cut from pay packages for workers who handle dangerous goods and other risky operations.

The strike coincides with the launch of the Australian Border Force, a single frontline operational border agency within the immigration department.

It also comes after a four-hour strike at Melbourne airport on June 25 meant hour-long queues to get through customs.

The union for Commonwealth workers is in a protracted pay dispute and it will receive a revised pay offer later this month.