Two others - another Singaporean and a Malaysian Airlines pilot - were also arrested in the last one week.

The crackdown appears to be confined to Australia, although arrests have been made from time to time elsewhere.

On Tuesday, for example, Italian police arrested a 55-year-old university professor after he stepped off a plane from Bangkok at Rome's Leonardo da Vinci airport. The arrest was part of a country-wide crackdown on child pornography.

In Dubai last November, a British Broadcasting Corporation (BBC) deejay was arrested for allegedly carrying pornographic DVDs into the country.

The Australian action appears to be a concerted effort aimed at stopping the smuggling of pornography into the country via Adelaide, according to a statement on the country's Customs website.

The website quoted Australian Customs national manager of investigations, Mr Richard Janeczko, as saying the department was seeing an increase in interceptions of objectionable pornography at the border.

Meanwhile, the SIA pilot at the centre of the porn storm, Captain Ng Kok Yauw, has arrived back in Singapore.

Contacted by The Straits Times yesterday evening, Capt Ng, 41, who has been flying with the airline for about 15 years, said: 'I am not in a good position to talk right now.'

The father of two, who has been described as a 'nice chap' and 'a regular family man' by colleagues, has been suspended by the airline pending investigations.

He was charged by Australian authorities on Monday and fined A$12,000 (S$15,241).

He pleaded guilty and paid the fine. Australian Customs Service, which arrested Capt Ng, said he was not charged with carrying child pornography, but provided no further details.

It is not a crime to bring pornographic material into Australia, according to a spokesman for the Australian Customs.

However, it becomes an offence when the materials are 'objectionable' or 'abhorrent', which includes child pornography.

The spokesman said the agency has seen an increase in the number of passengers and aircrew caught with pornography, but she did not have any statistics.

She said all travellers - whether passengers or airline crew - are subject to the same checks.

Captain P. James, president of the Air Line Pilots Association-Singapore, said: 'This is something that we can all learn from.

'We will not dispute that an offence has been committed but there is also no disputing that the man has already been punished for his offence.'

Capt Ng will not be flying until SIA completes its investigations, spokesman Stephen Forshaw said.

karam@sph.com.sg