But one of numerous Navsource ship's pages showing the vessel in precommissioned state, flying a US flag:
DDG-112 Michael Murphy. Scroll down. You'll find images of her on builder's trials flying the national ensign. As you've noted, it is for identification: http://www.navsource.org/archives/05/01112.htm
Commissioned ships fly a commissioning pennant, and in port, they fly the jack on the bow jack staff, as well as the national ensign. At sea, the ensign is flown from the main mast. In port, it is flown from the stern staff.
I was at the commissioning of USS Preble. They explained that--at its most basic essence--the commissioning of a US warship involves raising the commissioning pennant, and having the new commanding officer read his orders to assume command. Then, he declares he is taking command.
That's it. That is the all that is officially required. The captain reads his orders, then says, "I assume command." The pennant is raised. The instant it hits the top of the halyard, the ship is officially in commision.
Naturally, almost all of them add more ceremonies. Having the crew run aboard and "bring the ship to life" is one of the most common. And nearly anything else they want to add. Speeches by all sorts of dignitaries is also common. Walter Cronkite spoke at Preble's commissioning.
But, there are accounts from WWII particularly, where there simply wasn't time for a lot of ceremony. The crew mustered pierside, the captain read his orders and declared he was in command, the penannt went to the top of the halyard, and only a few dock workers saw anything. The ship sailed out of the harbor in commission.
The national ensign flying from a ship not yet in commission is fine.
After going thru my books and the book in question
about the Enterprise on page 14. To begin with . I dont think the flag is half mast. The main mast has a flag pole attached to the main mast that extends up at angle. This arrangement was common to the Lexington, Saragota ,and Yorktown. Old Glory has been raised up to the end of the pole where the top of flag is level to it. Since this a sea trials peroid on the next page 15 shows the same flag that day April 6,1938 having been repositioned to the top of the main mast.
So perhaps they were testing this.
Looking at other pictures of the Enterprise . The stars and stripes flew from the main mast pole as previous mentioned. Why would a a pre commissioned ship fly the country colors . I admit my guess is
indentification. So here's the Enterprise leaves Newport News Shipyard enters Chespeake Bay and then enters the Atlantic Ocean . While passing freighters that were entering Chespeake bay they
proabley communicated. I've been to navy commissioning cermonies and they use I think 3 flags in the cermony .One on the bow flag pole,main mast, and stern flagpole. Well there my answer . Look forward to hearing the positive or negative responses
The pic in question shows Enterprises port side on April 6, 1938. The caption states that it is before being commissioned but that the main mast has the American flag flying which was not to happen until commissioning. Now this is just a guess as I don't know the flag protocol of the Navy back then. I feel that something tragic must had happened as the American flag is being flown at half-mast and maybe a rule was changed just for that occasion. Just a guess on my part, Jon