The company said it had drawn up an action plan to improve driver availabilityTrain services have been disrupted across the West Midlands Railway (WMR) network because of a lack of available crew, the operator has said.
WMR posted warnings of disruption, external on the Snow Hill and Hereford lines, and its website, external said other routes covering Birmingham, Worcester, Kidderminster, Stratford, Leamington Spa, Redditch, Lichfield, Walsall and Nuneaton were affected.
After social media users complained, the company tweeted it had drawn up an action plan to improve driver availability.
The train drivers' union, Aslef, said the company needed to employ enough drivers.
The BBC has approached the rail operator for further comment.