The amount of time it takes for air mail to arrive depends on the starting and ending destination. Travel time and costs can be determined using the United States Postal Service website, which has a domestic and international price calculator.
Packages weighing up to 4 pounds can be sent via international delivery. The USPS refers to this service as First-Class Mail International, and it makes deliveries to 180 different countries.
Unless the destination country prohibits it, the USPS allows a Registered Mail option for First-Class Mail International. Certified and return-receipt mail also are allowed for those who need proof of delivery.