David Horne, Managing Director, LNER
Trains with cracks are to re-enter service after the rail industry assessed that the fault does not pose a safety risk.
Services on large parts of the network have been disrupted since Saturday after cracks were discovered in part of the chassis of several trains.
Manufacturer Hitachi, train operators and the Government have agreed a plan to reintroduce more Class 800 and 385 trains.
Andy Barr, CEO, Hitachi
Industry body the Rail Delivery Group (RDG) said engineers and independent experts have "completed rigorous tests and research" to get a "clearer understanding of the cracking issue".
The announcement means London North Eastern Railway and Great Western Railway will be able to ramp up services.
The service recovery plan has been overseen by regulator the Office of Rail and Road.
HM Chief Inspector of Railways Ian Prosser said the organisation will continue to "provide the rigorous oversight needed to make sure the right checks are being carried out".
GWR said the announcement means it can run "some additional services" on Thursday and introduce "more consistent robust timetables" after the weekend.
LNER said the return of its Class 800 Azuma trains will also not begin until next week.