Airmail to the states

I want to send a letter back across the pond-- will i get away with just putting 2 first class stamps on the envelope and writing "AIR MAIL" on it?

Possibly, but it's best to go to the post office and make sure you have the proper postage.   However, if you put your return address on the envelope, I've noticed that undeliverable mail usually gets returned.  I sent a letter to an address in the states that was undeliverable and it bounced all the way back to me in the UK!

I asked a postal employee at Christmas time because I was too lazy to wait in a long queue to weigh a christmas card I knew would require an £0.81 stamp and they confirmed that using multiple first class stamps to get to the required Airmail postage was fine.  Just weigh the letter and make sure that 2 first class is enough to cover the postage.  I have noticed that heavy greeting cards often break the £1.00 mark in postage.  I think a first class stamp is only worth £0.36 right now, so I would probably use 3 or 4 to be safe. 

I asked a postal employee at Christmas time because I was too lazy to wait in a long queue to weigh a christmas card I knew would require an £0.81 stamp and they confirmed that using multiple first class stamps to get to the required Airmail postage was fine.  Just weigh the letter and make sure that 2 first class is enough to cover the postage.  I have noticed that heavy greeting cards often break the £1.00 mark in postage.  I think a first class stamp is only worth £0.36 right now, so I would probably use 3 or 4 to be safe. 

I'm sure 2 will do me fine-- it's only me economic stimulus payment that was for some reason sent to me here, which I've now got to post to my parents to deposit in the states.  I think the cheapest airmail postage to the US is £.56