The teenage shot-stopper, who hails from Darlington, made his full debut in the U18 Premier League 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 in three UEFA Youth League fixtures for United's U19s.
Mair has represented England at U16 and U17 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.