If you travel regularly, you should renew your ESA letter with a licensed mental health professional at least once a year. Under the Air Carrier Access Act (ACAA) for emotional support animals, airlines can request up-to-date documentation from passengers who seek to travel with an emotional support animal. As the ACCA defines it, the current documentation is an ESA letter from a licensed mental health professional “no older than one year from the date of the passenger’s scheduled initial flight.”