So teacher I just finished my quiz for today, so I think the quiz is not hard, but I have a few question that I don't understand, like some time they gave you a question, and when you starting to answer the question you feel like they try to trick you and make you confuse too. I need you help me on this question the I don't know, today this question is Air travel became common after 1952, the year of (a / an / the) first commercial passenger jet flight. I chose the answer is ( an ), I don't know why I am wrong?  Can you help me to fixed.