"From Tuesday 4 January the Stansted Express train service between London Liverpool Street and Stansted Airport will operate at a reduced frequency.
Trains will depart London Liverpool Street at 25 and 55 minutes past each hour and wll call at Tottenham Hale, Harlow Town and Bishops Stortford.
Trains will depart Stansted Airport at 15 and 45 minutes past each hour and will call at Bishops Stortford, Harlow Town and Tottenham Hale.
In addition, the services between Stratford and Broxbourne, Hertford East and Stansted Airport will be suspended and passengers will be advised to travel on the half-hourly Airport services and change at Liverpool Street for Stratford instead.
Additional stops will be placed on our Hertford East services between London Liverpool Street and Hertford East for Northumberland Park and Angel Road. Full details will be found on the live travel update section of this website.
The reason for these timetable amendments is that some of our electric trains have suffered damage to their traction motors and electronic systems caused by the severity of the weather in recent weeks. To help in enabling our fleet engineers and technicians to repair this damage as quickly as possible, we intend to continue with this plan until further notice.
During this period, it is also possible that some of our other services across the National Express East Anglia network may operate with fewer carriages than normal.
We apologise to those passengers affected by these alterations. We are working as quickly as we can to bring trains back into service, with our engineers working around the clock to carry out the repairs and the situation regularly reviewed. Please bear with us as we proceed with this work to enable restoration of the full scheduled timetable. The changes we are implementing will enable us to provide the most reliable service in the meantime and give passengers clear guidance when planning their journeys."
http://www.nationalexpresseastanglia.com/rtti/amendments_to_stansted_airport_services