During the spring of 1919, the USS Aroostook was refitted as an "aircraft tender" to support the attempt by U.S. Navy naval aviators to fly across the Atlantic Ocean, which has never been done before, in three slow Curtiss NC floatplanes. The route for this attempt used southeastern Newfoundland and the Portuguese Azores Islands as stopping-off points for refueling and maintenance work on the planes, and for rest and mess periods for their aviators.
During the first half of May, 1919, the Aroostook was waiting at the port of Trepassey, Newfoundland, to serve as a floating base for the three medium-sized Curtiss NC floatplanes that took off from the New York City area on the 16th. After taking care of the Curtiss NCs and their crews, and seeing them off towards the Azores, the Aroostook next steamed to England, where she rendezvoused with the NC-4, the only airplane to complete the transatlantic flight, at the end of May. The crewmen of the Aroostook then disassembled the NC-4 and loaded her onto the ship for the voyage back to United States.
In August and early September, the Aroostook carried a cargo of naval mines and supplies to California via the Panama Canal. She spent the rest of the year on the West Coast carrying out transportation missions and also as the aviation flagship for the Pacific Fleet.
Though she continued to be classified as a "minelayer", and she received the warship designation CM-3 (minelayer) in mid-1920, the Aroostook's remaining active service was as an aircraft tender. Throughout the 1920s, she mainly served on the Eastern Pacific Ocean, but she made occasional voyages to the Caribbean Sea and the Atlantic Seaboard to take part in the annual, massive "fleet problem" exercises.
The Aroostook also steamed to Hawaii and back in 1925 and 1928, including on the first occasion as the support aircraft tender for a pioneering attempt to fly two patrol planes from the West Coast to Hawaii.