When the plane took off, it had only two engines. When it landed it had four.
Neither the couch that is shown damaged or the new couch are the same as the one typically used on set before or after this episode. The color is similar, but the fabric has a different texture and the arms are distinctly different.
Supposedly all of the family room furniture was outside when it rained, but only the couch was damaged. For instance, the Banks' chair is still in perfect condition.
While we know the furniture was damaged in the rain and it can be assumed that the floor was scuffed up by the dancers for the music video, it's never explained how the walls were damaged.