The correct answer is 'than the flight took off.' Key Points - No sooner is used to show that one thing happens immediately after another thing. - It is often used with the past perfect and usually followed by than. - Example: They had no sooner arrived than they were arguing. - Hence, 'than the flight took off' should be used to make the sentence grammatically correct. - Correct Sentence: No sooner did I arrive at the airport than the flight took off.