From an air traffic controller's perspective, that meant maintaining a safe distance between airborne aircraft.
( ( From ( ( an ( air ( traffic ( controller 's ) ) ) ) perspective ) ) ( , ( that ( ( meant ( maintaining ( ( a ( safe distance ) ) ( between ( airborne aircraft ) ) ) ) ) . ) ) ) )
(ROOT (S (PP (IN From) (NP (NP (DT an) (NN air) (NN traffic) (NN controller) (POS 's)) (NN perspective))) (, ,) (NP (DT that)) (VP (VBD meant) (S (VP (VBG maintaining) (NP (NP (DT a) (JJ safe) (NN distance)) (PP (IN between) (NP (JJ airborne) (NN aircraft))))))) (. .)))
The distance between airborne aircraft is kept safe by traffic controllers.
( ( ( The distance ) ( between ( airborne aircraft ) ) ) ( ( is ( ( kept safe ) ( by ( traffic controllers ) ) ) ) . ) )
(ROOT (S (NP (NP (DT The) (NN distance)) (PP (IN between) (NP (JJ airborne) (NN aircraft)))) (VP (VBZ is) (VP (VBN kept) (ADJP (JJ safe)) (PP (IN by) (NP (NN traffic) (NNS controllers))))) (. .)))