( ( ( The force ) ( that ( opposes ( ( the force ) ( of ( weight ( for ( an aircraft ) ) ) ) ) ) ) ) ( ( is lift ) . ) )
(ROOT (S (NP (NP (DT The) (NN force)) (SBAR (WHNP (WDT that)) (S (VP (VBZ opposes) (NP (NP (DT the) (NN force)) (PP (IN of) (NP (NP (NN weight)) (PP (IN for) (NP (DT an) (NN aircraft)))))))))) (VP (VBZ is) (NP (NN lift))) (. .)))
The force that opposes the force of weight for an aircraft is lift.
(ROOT (S (NP (NNP Weight)) (VP (VBZ is) (NP (NP (DT the) (NN result)) (PP (IN of) (NP (NP (DT the) (NN force)) (PP (IN of) (NP (NP (NN gravity)) (VP (VBG being) (VP (VBN opposed) (PP (IN by) (NP (DT the) (JJ normal) (NN force))))))))))) (. .)))