London Midland has cancelled 29 train services on Tuesday because drivers are refusing to work overtime.
The disruption is part of an ongoing workers' pay and conditions dispute and the worst affected route is from Birmingham New Street to London Euston.
Operations director Wallace Weatherill said staff training meant the firm was temporarily too dependent on overtime.
He said the company could not afford the £3m cost of giving staff equal holiday and pay.
Sunday Services have been disrupted by the dispute since 29 January and weekday services were also disrupted on 11 and 17 March.
The union Aslef is unhappy that drivers are on different terms and conditions.
London Midland was formed from Central and Silverlink in 2007 and operates services from the Midlands to London and the north west.
So London Midland has the money to pay the fines which will be imposed for cancelling the services, but they don't have money to pay the drivers?
