Airplane

We require $F_{net} = F_{thrust} - F_{air} = m \cdot \frac{dv}{dt}$ , where $v(t)$ is the velocity as a function of time. Since the plane's speed is constant (i.e. $v(t) = C$ ), the acceleration is zero ( $\frac{dv}{dt} = 0$ ). Thus $F_{thrust} = F_{air} = 3000N \Rightarrow F_{net} = \boxed{0N}.$