West Midlands Railway revealed a spike in work absences and admitted that last minute train cancellations, which can leave passengers stranded, are here to stay.
A WMR spokesman said: "The coronavirus pandemic is continuing to have a significant impact on our workforce.
"More recently, the Omicron variant has meant many colleagues are currently unable to attend work. While we are making every effort to run our planned services, some trains may be cancelled at short notice and we are reminding our customers to check before they travel."
The spokesman warned: "Some services on the Birmingham New Street to Shrewsbury line are likely to be cancelled. Please check the journey planner before travelling.
"We are keeping the situation under close review and it remains our intention to reinstate the full timetable on this line as soon as possible. Please check your train times before you travel."
In November the Star reported how passengers were getting stranded at stations including Wolverhampton, Codsall, Cosford, Albrighton, Telford and Shrewsbury as the last services of the night were being cancelled at short notice.
Holiday makers from the Black Country hoping to jet off from Birmingham International Airport will no longer have several services every hour to and from Birmingham New Street.
The WMT spokesman said: "From Monday, January 10, Birmingham New Street-Birmingham International shuttle services will become hourly Monday-Saturday. We are keeping the situation under close review and it remains our intention to reinstate the full timetable on this line as soon as possible."
WMT has scrapped trains on the Leamington Spa to Nuneaton via Coventry line until further notice
The spokesman said: "We are currently operating a rail replacement bus service on the Leamington Spa-Nuneaton via Coventry line until further notice. This is due to the impact of Covid-19 on our workforce. We are keeping the situation under close review and it remains our intention to reinstate the full timetable on this line as soon as possible. Bus times are in online journey planners now."
Campaign for Rail released data last month which detailed the sheer amount of services West Midlands Trains were cancelling at short notice at night, with the last service regularly not running. One Thursday in November saw 31 of the final 46 services on lines through Snow Hill Station, Birmingham, being cancelled at short notice.
Chairman Ian Jenkins criticised West Midlands Trains for not training enough new drivers during the pandemic compared to other rail operators.
He told the Star: "I think it would be wrong at the moment to criticise the railway industry as a whole right now. The impact of Covid is serious, and it may be getting worse.
"With 150,000 deaths in the UK, the worst in Europe, I wish all the staff working in rail the very best in getting back to health."
He added: "Campaign for Rail are not convinced, however, about the WMT commitment to services on the Nuneaton-Coventry-Leamington line, and we want to see an action plan for development on the route, as soon as conditions allow."