The problem is affecting services across much of the country, including Edinburgh, North Wales, Manchester, London and Southampton.
Services run by Virgin Trains, London Midland, CrossCountry and Arriva Trains Wales have all been hit by the issue.
No trains are running between Birmingham New Street and Birmingham International.
Network Rail said the disruption is expected to continue until 3pm.
Passengers travelling with Virgin Trains are being diverted via Stafford, extending their journey times by up to an hour.
CrossCountry services between Birmingham New Street and Reading are being diverted via Tyseley, south Birmingham.
Road transport has been requested to take airport passengers between Birmingham International and the city centre.
Some ticket restrictions have been relaxed in a bid to help travellers reach their destinations by other routes.