▁or ▁take ▁a ▁south west ▁tack . ▁Alt man ▁replied ▁" E ither ". ▁" Let ▁me ▁know " ▁was ▁the ▁response ▁from ▁the ▁tower , ▁with ▁Alt man ▁answering ▁" OK , ▁tell ▁you ▁what , ▁I ▁will ▁take ▁down ▁the ▁river ." ▁ ▁Alt man ▁was ▁then ▁instruct ed ▁to ▁contact ▁New ark ▁Liber ty ▁International ▁Airport , ▁a ▁directive ▁he ▁agreed ▁to . ▁However , ▁he ▁did ▁not ▁contact ▁the ▁tower ▁at ▁New ark . ▁It ▁later ▁trans p ired ▁that , ▁in ▁acknowled ging ▁the ▁instruction ▁to ▁contact ▁New ark , ▁Alt man ▁had ▁read ▁back ▁the ▁wrong ▁frequency ▁( 1 2 7 . 8   M Hz ▁instead ▁of ▁ 1 2 7 . 8 5 ), ▁an ▁error ▁that ▁the ▁controller ▁did ▁not ▁correct . ▁So on ▁after , ▁a ▁controller ▁at ▁New ark ▁who ▁was ▁concerned ▁about ▁aircraft ▁in ▁the ▁Pi per ' s ▁path ▁contact ed ▁the ▁T eter bor o ▁controller ▁and ▁asked ▁the ▁him ▁to ▁attempt ▁to ▁re - est ab lish ▁contact . ▁All ▁attempts ▁to ▁contact ▁Alt man ▁and ▁change ▁his ▁aircraft ' s ▁heading ▁were ▁un success ful . ▁After ▁the ▁failure ▁to ▁contact ▁Alt man , ▁a ▁rad ar ▁alert ▁about ▁a ▁possible ▁collision ▁occurred ▁in ▁both ▁the ▁New ark ▁and ▁T eter bor o ▁to wers . ▁However , ▁the ▁two ▁controllers ▁did ▁not ▁remember ▁seeing ▁or ▁hearing ▁this ▁alert . ▁ ▁While ▁heading ▁south ▁down ▁river , ▁the ▁air plane ▁was ▁seen ▁to ▁be ▁behind ▁the ▁sight