Frank Purdy Lahm was born on 17 November 1877 in Mansfield, Ohio, the son of balloonist Frank S. Lahm and Adelaide Purdy Lahm. Following his mother's death in 1880, Frank's father moved to Paris to pursue his ballooning interests, leaving his son in the care of a widowed aunt. Between 1880 and 1901, Lahm attended a number of schools and military institutes, finally graduating in 1901 with a Bachelor of Military Science degree from the United States Military Academy, West Point. After graduation, Lahm was assigned to the cavalry branch and immediately departed to the Philippines for duty with the Sixth Cavalry. He served there until 1903, when, much to his dismay, he was reassigned to West Point to teach French. In the summer of 1904, Lahm went to visit his father in Paris on leave. While there, Lahm made his first ascent in a balloon. One year later Lahm was awarded Fédération Aéronautique Internationale (F.A.I.) Balloon Certificate #4. In 1906 Lahm represented the United States in the first Gordon Bennett International Balloon Race, which Lahm and his aide, Major Henry Hersey, won after out distancing their nearest opponents by fifty miles. Lahm was then transferred to the Aeronautical Section of the Army Signal Corps. Lahm was ordered to investigate aeronautical activities in Britain and Germany, where he spent much of 1907. In February of 1908, Lahm drafted a report on military aviation and presented it to Theodore Roosevelt, who then approved a sum of $25,000 for military aeronautics. Having received F.A.I. Airship Pilot Certificate #2, Lahm was deemed the best candidate to direct trial flights leading to the possible purchase of military aircraft.
With his prior aviation experience, Lahm was put in charge of organizing the 1908 trials of the Wright brothers' aircraft at Fort Myer, Virginia. While at Fort Myer, Lahm was the first passenger in a heavier-than-air craft, flying eight days prior to the accident in which Lt. Thomas Selfridge became the first Army flight casualty. After the accident, Lahm and the other directors were re-assigned to their original branches, with Lahm returning to the cavalry. Trial flights of the Wright Military Flyer resumed in 1909. On 9 September, Lahm and Orville Wright set the world endurance flying record with a flight of six minutes. During October, Wilbur Wright taught Lahm and Lt. Frederick Humphries to fly at College Park, Maryland, and Lahm received F.A.I. Airplane Pilot Certificate #2 on 26 October, soloing three minutes after Humphries.
Following the successful trial flights, Lahm returned to the cavalry branch and remained in relative anonymity until July 1911, when he won the National Balloon Race in St. Louis, Missouri, and placed second in the International Balloon Race, held at the same time. On 18 October, 1911, Lahm married Gertrude Jenner. In 1912, Lahm was transferred to the Philippine Islands, where he established and commanded the U.S. Army Flying School at Fort McKinley. Lahm remained in the Pacific until 1914, when he was again reassigned to the cavalry and served on the Mexican border. After his tour with the cavalry, Lahm was promoted to the rank of captain in April of 1916 and served as the secretary of the U.S. Army Flying School, Rockwell Field, San Diego, California. He remained here until 1917, when he was put in command of the U.S. Army Balloon School, Omaha, Nebraska, and promoted to the temporary rank of colonel. Later in that same year, Lahm was ordered overseas to observe British and French use of balloons in combat. Originally intending to return home, Lahm was then put in command of the American Expeditionary Force (A.E.F.) lighter-than-air service. He also acted as Commander of the Second Army Air Service, A.E.F. In 1918, due to the wartime necessity for officers, Lahm was promoted to the permanent rank of colonel and continued his service with the Second Army Air Service.
In 1919 and 1920 Lahm attended the Army War College, followed by assignment to the War Department General Staff in Washington, D.C. until 1924. From 1924 to 1926 Lahm acted as Air Officer for the Ninth Corps Area, and in 1926, Lahm was instrumental in planning and organizing the Air Corps Training Center, which was to soon become Randolph Field, San Antonio, Texas. His duties at Randolph Field kept him in Texas until 1930, when Lahm was temporarily promoted to the rank of brigadier general and assigned as the Assistant Chief of the Air Corps. In 1930, Lahm returned to the position of Air Officer, Ninth Corps Area. In 1931, Lahm's wife died. Following his duty as Air Officer, Lahm reverted to his permanent rank and was assigned as the Air Attaché to France, Belgium, and Spain. In 1933, Lahm picked up the additional responsibility of being Military Attaché to France and Belgium, remaining in both of these posts until 1935. He then served as Air Officer for the Second Corps Area until 1940, when he became the Chief of Aviation, First Army, at Governors Island, New York. In 1941, Lahm was promoted to the permanent rank of brigadier general and assigned as the Commanding General at the Gulf Coast Training Center, Randolph Field, Texas. While here he received an honorary promotion to the rank of major general from President Franklin Roosevelt. Having reached mandatory retirement age, Lahm retired on 30 November, 1941 with the rank of brigadier general.
Following retirement, Lahm moved back to his hometown of Mansfield, Ohio. His interest in aviation continued, and within two years he and Charles de Forest Chandler co-authored How Our Army Grew Wings, on aeronautical activities in the U.S. Army prior to 1914. Lahm also became interested in civic activities during this time, becoming involved with the Boy Scouts, various local historical societies, and with stimulating local interest in international events. He helped establish International Affairs Committees in Cleveland and Mansfield, Ohio. Lahm also spoke on the lecture circuit, relating his personal experiences and providing support for the advancement of military aviation. On 4 April, 1948, Lahm married Grace Wolfe Kenson.
On 3 July, 1963 Lahm suffered a stroke and was hospitalized in Sandusky, Ohio. On 7 July 1963 he passed away at the age of eighty-five. His body was cremated and the ashes were spread into the air from a plane flying over Randolph Field, Texas.
In addition to being a member and past President of the Early Birds of Aviation, Inc., Lahm was also a member of the Washington, D.C. Army and Navy Club, the National Aeronautical Association, the American Legion, the Aéro-Club de France, and an Honorary Member of the Aero Club of America. Besides his many balloon competition victories, his awards include the Distinguished Service Medal (U.S.A.), the Commander of Legion of Honor (France), and the Ordre d'Avis (Portugal).