They had been responding to a report about an aircraft that did not exist.
( They ( ( had ( been ( responding ( to ( ( a report ) ( about ( ( an aircraft ) ( that ( ( did not ) exist ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (PRP They)) (VP (VBD had) (VP (VBN been) (VP (VBG responding) (PP (TO to) (NP (NP (DT a) (NN report)) (PP (IN about) (NP (NP (DT an) (NN aircraft)) (SBAR (WHNP (WDT that)) (S (VP (VBD did) (RB not) (VP (VB exist)))))))))))) (. .)))
The report had been misread when it was given.
( ( The report ) ( ( had ( been ( misread ( when ( it ( was given ) ) ) ) ) ) . ) )
(ROOT (S (NP (DT The) (NN report)) (VP (VBD had) (VP (VBN been) (VP (VBN misread) (SBAR (WHADVP (WRB when)) (S (NP (PRP it)) (VP (VBD was) (VP (VBN given)))))))) (. .)))