“When pigs fly” is an idiomatic way of saying that something will never happen. Pigs are heavy animals, without wings, and cannot possibly fly. So “when pigs fly” is a time that will never come. The phrase is used for humorous effect to scoff at someone’s intentions to achieve or carry out something which is beyond their previous efforts and accomplishments, especially in politics. There are numerous variations on the theme; when someone with a reputation for failure finally succeeds, onlookers may claim sarcastically to see a flying pig.
Yeah yeah yeah, the person who wrote that has obviously not been around – come to Kuching and my car and you will see a flying pig.
Flying and carrying a passenger even !