"After sailing more than 27,000 nautical miles" is the dependent clause
Explanation:
The dependent clause is the part of a sentence that establishes a dependent relationship with the main clause, also called an independent clause. This is because the dependent clause does not have the ability to expose a message alone, as it does not have the full meaning, per se. This clause needs a complement so that it can be understood and that complement is the independent clause. As you can see, the "After sailing more than 27,000 nautical miles" clause is unable to give meaning, so the clause is dependent.
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