The highly-rated goalkeeper, who hails from Darlington, made his full debut in the Under-18 Premier League as a 15-year-old during a 3-3 draw against Leeds United in April 2025.
Last season, Mair made ten appearances across all competitions for Chris Moore's side as well as featuring in-between the sticks for three UEFA Youth League fixtures for United's Under-19s.
Mair has represented England at Under-15, Under-16 and Under-17 level, making his international debut for the latter age group shortly before his 16th birthday in a 2-1 friendly win against Venezuela.
The young 'keeper made his first start for United's Under-21s side during a National League Cup clash against Tamworth in August 2026 as a 16-year-old.