To avoid New York area air traffic and uncertain about what to do, the fighters were brought down to military airspace to hold as needed.
( ( To ( avoid ( ( New York ) ( ( ( area ( air ( ( traffic and ) uncertain ) ) ) ( about what ) ) ( to do ) ) ) ) ) ( , ( ( the fighters ) ( ( were ( ( ( brought down ) ( to ( military airspace ) ) ) ( to ( hold ( as needed ) ) ) ) ) . ) ) ) )
(ROOT (S (S (VP (TO To) (VP (VB avoid) (NP (NP (NNP New) (NNP York)) (SBAR (WHNP (NP (NN area) (NN air) (NN traffic) (CC and) (NN uncertain)) (WHPP (IN about) (WHNP (WP what)))) (S (VP (TO to) (VP (VB do))))))))) (, ,) (NP (DT the) (NNS fighters)) (VP (VBD were) (VP (VBN brought) (PRT (RP down)) (PP (TO to) (NP (JJ military) (NN airspace))) (S (VP (TO to) (VP (VB hold) (ADJP (RB as) (VBN needed))))))) (. .)))
To avoid air traffic in new York and not knowing what to do, fighters were sent to military air space. 
( ( ( ( To ( ( avoid ( air traffic ) ) ( in ( new York ) ) ) ) and ) ( not ( knowing ( what ( to do ) ) ) ) ) ( , ( fighters ( ( were ( sent ( to ( military ( air space ) ) ) ) ) . ) ) ) )
(ROOT (S (S (S (VP (TO To) (VP (VB avoid) (NP (NN air) (NN traffic)) (PP (IN in) (NP (JJ new) (NNP York)))))) (CC and) (S (VP (RB not) (VBG knowing) (SBAR (WHNP (WP what)) (S (VP (TO to) (VP (VB do)))))))) (, ,) (NP (NNS fighters)) (VP (VBD were) (VP (VBN sent) (PP (TO to) (NP (JJ military) (NN air) (NN space))))) (. .)))