USPS First Class International Mail postal service?

Using USPS First Class International Mail, how long would it take to get from the USA to South Australia, Australia? Please Helep!USPS First Class International Mail postal service?
First class air mail from the United States to other countries takes 14-21 business days, according to the post office. Sometimes customs will delay this time frame.USPS First Class International Mail postal service?
i would say a week at the least, and 2 weeks at the most.