The correct answer to this open question is the following.
There is no question here, just a statement.
If this is a true or false question, then the answer is "false."
It is false that service was the exclusive responsibility of the Post Office until 12 August 1918 when the United States War Department joined the Post Office to furnish the planes and pilots.
The truth is that the US Army had supervised for three months the operations of the air mailing service. It started on May 15, 1918, and after the successful operations and barely any incidents, the Army left and gave total control of the operation to the United States Postal Service.
Planes took off from the Polo Grounds in Washington D.C. and Belmont Park, in Long Islands, New York.