Lets take a look at the jet example from another perspective. The jet is self assembled by proxy of humans being self-assembled. A 747 is the result of a trill

Lets take a look at the jet example from another perspective. The jet is self assembled by proxy of humans being self-assembled. A 747 is the result of a trillion step chemical reaction that stretches across the history of life on earth itself. The chances of this reaction self-assembling on another planet under the same conditions and in the same manner are impossibly low. What we don't know is whether or not the chemical reactions forming the first life form on earth happened in the same improbable way. Did it happen over eons? did it require a billion steps? I dunno. Nobody knows. It is not unrealistic to say that the chemical reactions necessary to form life are so rare that earth is the only planet in the universe with life.