WASHINGTON, Aug 5 (Reuters) - The Federal Aviation Administration (FAA) on Thursday issued a new safety directive for Boeing (BA.N) 737 Next Generation (NG) and MAX airplanes to address a potential issue with reduced fire suppression capabilities. The FAA said planes may have a failed electronic flow control of the air conditioning packs that vent air into the cargo hold from other areas of the plane. The directive prohibits operators from transporting cargo in the cargo hold if airplanes are operating with this condition unless they can verify items are nonflammable and noncombustible. The FAA said the directive covers all Boeing 737 8, 737 9, and 737 8200 MAX airplanes and some 737-800 and 737-900ER series airplanes. Boeing did not immediately comment. The airworthiness directive impacts 663 airplanes registered in the United States and approximately 2,204 worldwide. Operators must comply with this directive beginning 10 days after date of publication.