Thomas was born in North Shields on 2nd October 1895. He was the youngest son of Thomas Finkall Blair Sr., a Coal Trimmer, and Sarah Jane Blair (née Johnston). His parents married in 1893. Thomas had one brother, Robert Johnston, and four sisters, Mary Ann, Margaret Johnston, Jemima Weatherstone and Catherine Ann.
Thomas was educated at Trinity Public Elementary School in North Shields, then Tynemouth High School between 1909 and 1913, where he was elected Kettlewell Scholar in 1911. He trained to be a teacher at Armstrong College 1914/15.
Thomas joined the Northumberland Fusiliers, 6th Battalion, on 13th July 1915, at the rank of Private. He embarked from Southampton on 10th November 1915, disembarking in Le Havre, France. On the 23rd February 1916, he was charged with “losing by neglect one smoke helmet” (cost 4/6).
Thomas received a gunshot wound to the forearm on 15th July 1916. He was transferred back to the 4th Northern General Hospital in Lincoln on the 18th July, where he stayed until 4th August 1916. He was then transferred to Northumberland Fusiliers Reserve, 4th Battalion, on 1st September 1916, receiving the service number 265967. On 23rd November 1916, he embarked from Folkestone and disembarked in Boulogne. He was then posted to 6th Battalion on 6th December 1916. On 26th September 1917, he was granted a commission and transferred to the Royal Flying Corps at the rank of Second Lieutenant. The Royal Flying Corps became the Royal Air Force on 1st April 1918.
Thomas was killed on 6th April 1918 at the age of 22. He died in Stamford, Lincolnshire, following a flying accident in RE8 biplane, serial number B7683, of No. 5 Training Depot Station. At the time of his death, he was based at the Training Depot Station in Lincolnshire. On 8th April his death was announced in the local Shields Daily News.