The incident means there are no services to Fleet, Winchfield or Hook – the stations between Farnborough and Basingstoke – to the north of Southampton.
But it is also having a knock-on affect on other services.
Southampton is Guernsey’s second most important air link after Gatwick, with more than 90,000 travellers using it last year. There are also services between Southampton and Alderney.
Aurigny has issued a warning to travellers.
‘We are advising all passengers planning to travel with us from Southampton to allow extra time to complete your journey to the airport to ensure that you arrive on time for your flight, or to use alternative transport,’ a spokesman said.
South Western Railway operates services on this part of the rail network and warned there would be disruption until at least Sunday, with trains travelling north of Southampton Airport towards London Waterloo terminating at Basingstoke.
An extremely limited shuttle is meant to run between Basingstoke and Woking, and passengers are advised against all but essential travel on services which would usually pass through the area.
The embankment near Hook consists of a mixture of London clay and other local soils, which had been saturated after days of heavy rain.
The slip happened when the soil gave way along a 44m section of 10m-high embankment, sliding out from underneath the tracks.
The slip has left one track hanging in mid-air and another damaged. There are four tracks in this area, but only two London-bound lines are passable.
Network Rail Wessex route director Mark Killick said this was a huge landslip.
‘We will need to stabilise the embankment, essentially stopping it moving, and then rebuild the railway where it has slid away,’ he said.
All trains between Southampton Airport and London Waterloo were being listed as cancelled yesterday on the journey planner.
Services were listed as running today, but with warnings of major disruptions, so it is unclear if these will operate.
It is possible to get from Southampton Airport to London via Southampton Central and Fratton, but this requires two train changes, a more expensive ticket and turns a 70-minute direct journey into a two-and-a-half hour trip.
The landslip is also affecting rail services from London to Exeter, as well as services to Southampton and Weymouth from London.