AA doesn't require an actual form, they will accept a letter from your vet. It is req'd b/c of the low temps in Bos at this time of year.
Per aa.com, the letter must include the following:
The restriction for cold temperature restriction may be waived with a written veterinarian statement. The low temperature acclimation certificate/statement/form must include the following:
* Name and address of the passenger
* Name of the animal
* Name and signature of licensed veterinarian
* Veterinarian's accreditation date and number
* Temperature which the animal is acclimated
* The letter must be dated within 10 days of the first flight the animal will be on and within 30 days of any subsequent travel within the same itinerary. It may be necessary for a passenger to obtain an additional letter for a lengthy trip
When temperatures fall below 20 degrees Fahrenheit ((-6.6 degrees C), pets may not be checked even with a statement of low temperature acclimation.