I wish they would have let people evacuate the airplane from which ever exits were available even though all four exits might not have been checked for safety first.
この場合、次のような言い方ができますよ。
ーI wish they would have let people evacuate the airplane from whichever exits were available even though all four exits might not have been checked for safety first.
「４つの非常口すべての安全がまず確認されていなくても、可能な非常口から飛行機から避難させてほしかった」
to let people evacuate「人々を避難させる」
to checked for safety「安全を確認する」
ご参考まで！
I wanted them to let us evacuate through any available exit.
I wanted them to let us evacuate through any available exit.
They should have let us escape through the exits that were safe to use.
「利用可能な出口から避難させてほしかった」
「安全に使える非常口から逃がすべきだった」
・Evacuate / Escape
「避難させる」は evacuate が公式な場面でよく使われる単語です。命を守るために「逃げる」という切実なニュアンスなら escape も自然です。
カナダ 
アメリカ合衆国 
