The airplane can simply be regarded as a way of thinking that pertains to a plan. It also reflects a way of thinking that appears quite intelligent or spiritual. Here the plan may relate to the idea of being economical as the destination is Scotland. {A common stereotype associated with the Scots is that they tend not to be very free spenders.}

Where the plane manages to land safely on the ground, the plan can be seen as having been successful and having justification on rational grounds of reasoning. Here this reasoning would relate to Scottish thinking. As your plane just misses a few roofs of houses, it seems that your plan to be economical is in danger of clashing with an economical mental attitude that may not seem as intelligent but based on solid ground/reality. 

The scene shows that a way of thinking pertaining to being very economical has encountered a serious obstacle ? one which may relate to the idea of the bar having been raised, i.e. the task having been made more difficult than was expected. (the building has a metal bar joined to the back we hit this and the plane goes down) The plane going down would suggest the plan cannot be carried out as was expected or it simply isn?t working.

By jumping off the low flying plane, it may imply that you have to take a leap of faith when ceasing to use the plan. While the plan does not exactly ?go down in flames?, i.e. it does not fail spectacularly, it does go up in flames somewhat in future (the plane burst into flames and crashes further on ), i.e. the plan comes to a sudden and complete end.