In an essay I am working on, I am writing letters between two sisters. One lived in New York and the other lived in London during the time of 1919. I need to figure out the amount of time it took for a letter to be sent from New York and arrive in London, and the approximate time it would take for the letter to be received and a reply sent back to New York in that time period, so I can get somewhat accurate dates for the letters. Thank you to all who answer.
A quick check of the Blue Riband crossing times shows that the fastest vessels were crossing the Atlantic in just under 5 days (in either direction) by 1919. The average crossing time would probably be around a week. So allowing for delivery inland, writing an immediate reply and meeting a returning ship, the sender would probably be waiting in the region of 15-16 days for the reply.