Both these tenses are correct. 1.When the speaker thinks as stated in the sentence is true or the fact that there are likely to occur or, as the if clause with the indicative mood. 1)It sounds as if it is raining. 2)He talks as if he is drunk. 2.When the speaker thinks as stated in the sentence is not true or possible or rarely exist, as the if clause in subjunctive mood. Said, in contrast to the fact now, using the past tense of the verb. 1)You look as if you didn’t care. Representation and the fact that in the past or talk with time on the contrary, the predicate verb "had + past participle". 2)He talked about the Great Wall as if he had been there before.

You really need a continuous form here e.g. in the present: I feel as if I'm flying. In the past: I felt as if I was flying.