A worldwide outage to passenger processing systems has left flights on the tarmac and passengers unable to check in.

Major airlines around the world were briefly hit by computer problems due to an issue with a system from Spanish travel technology firm Amadeus.

Passengers at Sydney, Melbourne, London Gatwick, Charles de Gaulle in Paris, Reagan Airport in Washington DC, Changi Airport in Singapore, Johannesburg and Zurich airports have all reportedly had problems.

A Qantas spokesperson confirmed that there had been a systems outage but said that flights were continuing to depart from Sydney Airport.

A Melbourne Airport spokesperson confirmed there had been an outage to the airport's advanced passenger processing system which was operated by the Department of Immigration and Border Protection.