A simple question

Hi everybody,

I was chatting with a scottish friend last week and he was telling me about a trip to London he was planning, so I asked him if he had already bought the plane tickets. The thing is I wasn´t sure if the tense I used to formulate the question was correct. My question was: Did you buy the tickets to London?--- I used the simple past tense but right afert I finished I started thinking why I didn´t use the present perfect tense. What would the correct question be in that situation: Did yo buy the tickets? or Have you bought the tickets??
I apologize for the simplicity of my question but after several years of being an english student I still get confused on the correct use of these two tenses.

Thanks.