Philip wants to reproduce and sell copies of two airline posters he has collected, one is dated 1951 and includes copyright notification, and the other is dated 1940. Philip asks if he can legally do so and if the copyrights have been renewed, and how he would know.
Philip, I have this handy article, "When Copyright Protection Becomes Public Domain." You may also want to read, "Can I Search The Copyright Office?" to learn how to check on a work.
You have entered that grey area of works dated between 1923 and 1964. When the answer is no or maybe, and the burden of proof is on you, and don't risk it for commercial ventures. In your case there is a company name on the posters, and you might have to contact them under copyright law to find out what the status of the rights are, that's called diligent search. So for you the answer is no, not without checking and/or asking permission.
Very interesting. We also have some of this kind of question being submitted to us. Also, at Patent Agents there is information which relates to this. However, we only do patent work and not copyright. Copyright has become complex with the internet. We’ll figure it out.