The identification required depends on whether you are flying domestically or internationally.
Domestic Travel
When travelling on a domestic flight, you may need to show photographic identification, but you may not necessarily need a passport. Please note that determining whether you require a passport or not for domestic travel is your responsibility.
International Travel
You will always require a passport for international flights, typically one that is valid for at least six (6) months from the date of return. Some countries may also require passports to be machine-readable. It is your responsibility to check the requirements of the countries you are transiting and visiting.