All US passengers over the age of 18 must show a state or government issued photo identification card at the time of check-in. Non-US passengers over the age of 18 must show a valid foreign government-issued passport at the time of check-in. Children under the age of 2 must have proof of age in the form of a passport or birth certificate. Passengers between the ages of 2 and 18 are not required to present identification, but must be accompanied by an adult 18 years of age or older.