14 CFR § 61.49 - Retesting after failure.
(a) An applicant for a knowledge or practical test who fails that test may reapply for the test only after the applicant has received:
(1) The necessary training from an authorized instructor who has determined that the applicant is proficient to pass the test; and
(2) An endorsement from an authorized instructor who gave the applicant the additional training.
(b) An applicant for a flight instructor certificate with an airplane category rating or, for a flight instructor certificate with a glider category rating, who has failed the practical test due to deficiencies in instructional proficiency on stall awareness, spin entry, spins, or spin recovery must:
(1) Comply with the requirements of paragraph (a) of this section before being retested;
(3) Demonstrate satisfactory instructional proficiency on stall awareness, spin entry, spins, and spin recovery to an examiner during the retest.