Is it were still alive or was still alive?

Answer 1

The subjects I/He/She/It use "was" whilst the subjects We/They/You use "were".

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In correct English grammar (which most modern speakers of English are sadly not taught) the subjunctive case takes the plural. "Subjunctive" means situations of hope, possibility, condition, supposition, intention or wish, often using the word "if" to introduce the clause:

If I were a rich man (not If I was . . .)

If I were rich (not If I was . . .)

Supposing he were a policeman (not supposing he was . . .)

She wished she were an actress (not she wished she was . . .)

So in an active clause the singular "was" is correct: "He was surprised to find that he was still alive after the plane crash".

But in a subjunctive clause it is always "were": If the plane were to crash and he were still alive, he would be surprised".

Answer 2

The correct phrase is "if he/she were still alive." This is because "were" is used in hypothetical situations, such as imagining the person being alive in this case. "Was" is used for statements about something that actually happened in the past.