How to correct my advisor's English? I've noticed that my advisor (non-native) sometimes makes minor spelling/grammatical errors in academic papers. I believe this is due, in part, to the fact that until very recently, nobody in the lab was a native speaker.

Is there a way that I can bring this to my advisor's attention professionally? I would like to also let him know that I'd be happy to proofread any of his papers prior to submission, if he would like. Obviously, I make mistakes as well, so I'm sure I will make similar errors at some point in publications, but I would always want someone to point it out to me.

Edit: I should note that I have no intention of trying to correct his spoken or informal English.
Some non-native speakers of English are eager to improve their English and grateful for corrections. Others have, unfortunately, a very different attitude.  Ahmad correctly suggests caution if your adviser is easily offended, but it may be difficult to determine whether he's easily offended. So I'd suggest beginning with just one of your adviser's errors, perhaps a spelling error where it's easy to check in a dictionary that it really is an error.  See how he reacts to that before correcting more errors.