Passage: Concerned about relying upon commercial airlines to transport the president, USAAF leaders ordered the conversion of a military aircraft to accommodate the special needs of the Commander-in-Chief. The first dedicated aircraft proposed for presidential use was a C-87A VIP transport aircraft. This aircraft, number 41-24159, was modified in 1943 for use as a presidential VIP transport, the Guess Where II, intended to carry President Franklin D. Roosevelt on international trips.  Had it been accepted, it would have been the first aircraft to be used in presidential service. However, after a review of the C-87's highly controversial safety record in service, the Secret Service flatly refused to approve the Guess Where II for presidential carriage. As the C-87 was a derivative of the Consolidated B-24 Liberator bomber, it presented strong offensive impressions to enemy fighter aircraft as well as foreign destinations visited, an issue not present with airplanes that were used purely for transport. The Guess Where II was used to transport senior members of the Roosevelt administration on various trips. In March 1944, it transported Eleanor Roosevelt on a goodwill tour of several Latin American countries. The C-87 was scrapped in 1945.The Secret Service subsequently reconfigured a Douglas C-54 Skymaster for presidential transport duty. The VC-54C aircraft, nicknamed the Sacred Cow, included a sleeping area, radio telephone, and retractable elevator to lift Roosevelt in his wheelchair. As modified, the VC-54C was used by President Roosevelt only once before his death, on his trip to the Yalta Conference in February 1945.Sacred Cow is now on display at the National Museum of the United States Air Force at Wright-Patterson AFB, Ohio.

Question: What is the nickname of the VC-54C aircraft?
the Sacred Cow