Quote:
Can you use say a 45 cent air mail stamp as mail now. Will the post office take it?
Yes, all US airmail stamps are still valid for any class postage. The 1968 Airlift stamp (not classified as an airmail stamp by Scott) is also valid for postage.
All the 45c airmail stamps are tagged, so you should not have any problems with the automated canceling/sorting machinery kicking it out.