Physics help please! What did I do wrong?

hmm.... I don't really get how we are supposed to answer this question from the given information. You want the weight of the plane? So from your calculation you are saying that the acceleration is 0? because that is the only way that the Fg=ma. That doesn't make sense though unless the plane is already moving and you are saying that this is at takeoff. At takeoff, a plane accelerates. You need the acceleration of the plane to solve this problem...