According to Official Guinness Records,
The earliest solo transatlantic flight was achieved by Capt. (later Brig. Gen.) Charles Augustus Lindbergh (1902-74) who took off in his 165kW 220-hp Ryan monoplane Spirit of St Louis at 12:52p.m. GMT on 20 May 1927 from Roosevelt Field, Long Island, New York, USA. He landed at 10:21p.m. GMT on 21 May 1927 at Le Bourget Airfield, Paris, France. His flight of 5810km 3610miles lasted 33 hours 30 minutes 29.8 seconds, so winning a prize of $25,000. The aircraft is in the Smithsonian Institution, Washington, DC, USA.
For a complete list of 1927 records, please visit 1927 Guinness Records in France.