The exact rate depends on your destination. The airmail postage for a one ounce letter is 75 cents to Canada, 79 cents to Mexico, and 98 cents to other countries.
There is no special airmail rate. For the price of a regular first class stamp, 44 cents, any letter being sent out of state will automatically be sent via air.
USPS charges $0.98 for a one-ounce airmail letter to most international destinations. That same letter would cost $0.75 to send to a destination in Canada and $0.79 to send to Mexico.
