"I love you" 出现在天上的英文表达方式可能是 "I love you appears in the sky"。这句话的来源可能是某个人将 "I love you" 写在飞机上的广告牌或者某个人在天空中放飞气球或旗帜，使得 "I love you" 出现在天空中。

一些英文例句及其中文翻译如下：

"I saw 'I love you' written in the sky last night and it made my day."
"昨晚我看到天上写着 'I love you'，这让我开心了一整天。"

"I can't bepeve you wrote 'I love you' in the sky for our anniversary. That's so romantic!"
"我真的不敢相信你为了我们的纪念日在天空中写了 'I love you'。太浪漫了！"

"I wish I could write 'I love you' in the sky for everyone to see. Love is such a beautiful thing."
"我希望能够在天空中为所有人写下 'I love you'。爱是如此美妙的东西。"