61.3 Requirement for certificates, ratings, and authorizations.
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(2) Except as provided in paragraph (d)(3) of this section, no person other than the holder of a flight instructor certificate issued under this part with the appropriate rating on that certificate may --
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(ii) Endorse an applicant for a --
(A) Pilot certificate or rating issued under this part;
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§ 61.41 Flight training received from flight instructors not certificated by the FAA.
(a) A person may credit flight training toward the requirements of a pilot certificate or rating issued under this part, if that person received the training from:
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(2) A flight instructor who is authorized to give such training by the licensing authority of a foreign contracting State to the Convention on International Civil Aviation, and the flight training is given outside the United States.
(b) A flight instructor described in paragraph (a) of this section is only authorized to give endorsements to show training given.
In other words: foreign flight instructors can give you training time, but not endorse you in any way for anything...
regards
Patrick