This is just an idea I had after watching The Avengers one night. What if, instead of Barton only taking out two of the four turbines on the S.H.I.E.L.D helicarrier, he was instructed to take out all four? The helicarrier drops, and what if, because of this mistake, the candidates for the Avengers are lost? The Chitauri invasion still threatens the Earth, and with no heroes to protect it, will the planet fall?