On 29 September 2015, the IRS released Draft Form 8809-I (Link) with instructions (Link). Form 8809-I is used to request an initial or additional extension of time to file Form 8966 “FATCA Report” (Link) for the current tax year and should be filed before the due date of Form 8966.
The draft instructions state: File Form 8809-I as soon as you know an extension of time to file is necessary, but not before January 1 of the filing year. Form 8809-I must be filed by the due date of Form 8966. The due date for filing Form 8966 is March 31 of the year following the year to which the Form 8966 relates, unless you are an FFI reporting under a Model 2 IGA (reporting Model 2 FFI) with a different reporting date specified in the applicable Model 2 IGA. If you are requesting an additional hardship extension, Form 8809-I must be filed by the first extended due date of Form 8966.