TRAIN services to and from the Highlands were cancelled due to a line closure for "safety reasons" caused by "heavy flooding".
Some 110 yards of the tracks were flooded near the Slochd summit between Aviemore and Carrbridge.
The 8.45am train from Glasgow Queen Street due in Inverness at 12.07pm, was one of the first to be cancelled.
On the Highland Main line, trains to and from Edinburgh and Glasgow were could not get further north than Aviemore.
ScotRail were forced to draft in replacement buses to run a shuttle service between Aviemore and Inverness.
One of the two lines was later re-opened, but there is a 5mph speed restriction and services continue to be disrupted. But a second line of track at the scene, the down loop, remained closed.
The flooding follows snowfall in the Cairngorms and heavy rain.
Services were expected to continue to be disrupted until 3.15pm but the deadline was further extended to 4.15pm.
In a separate incident, the line between Glasgow and Oban had to be closed for safety reasons leading to further service cancellations due to a broken rail at Taynuilt Trains were halted between Oban and Crianlarich after the damaged rail was reported, with disruption expected to continue until 5pm.
UPDATE: Here's what the @NetworkRailSCOT team are dealing with. pic.twitter.com/32pDdXJMFB
— ScotRail (@ScotRail) November 12, 2019
The latest disruption comes after hundreds of train services on the Glasgow to Edinburgh line and the world-famous West Highland Line were estimated to have been cancelled in August as engineers continued to deal with flooding issues.
In the latest flooding disruption, Network Rail Scotland said a section of the mainly single-track line was flooded at the 1,315ft summit, the second highest on the route.
A Network Rail Scotland spokesman said: "At 08:10am it was reported that there was standing water covering a 100m stretch of the Highland Main Line at the north end of Slochd loop "The line was closed as the water was at the height of the rail head in places and had also submerged a set of points.
"We currently have engineers on site inspecting the track and were able to reopen the main line at a reduced speed at 10:25am, but the down loop remains closed as water is continuing to flow into that area of the track.
"Our engineers are working to fully reopen the line as quickly as possible for our customers.
"Flood waters can pose a real danger to rail safety – dislodging the track bed or damaging signalling systems.
In August, hundreds of Glasgow to Edinburgh services were estimated to have been cancelled over three days as torrential rain twice flooded Winchburgh Tunnel in West Lothian.
Continuing issues arose despite Network Rail Scotland, which is responsible for the infrastructure of the rail network, renewing the track, and drainage systems, through Winchburgh tunnel in 2015 meaning there were pumps built in which begin to pump water out automatically when it starts to build up.
At the same time it was estimated that more than 120 West Highland Line services, including the daily Caledonian Sleeper services to Fort William, were disrupted in the eight days since a section was shut last week after it partially collapsed.
Network Rail had to deal with problems caused after miles of track which became submerged or washed away near Inverness, Carrbridge, Ardlui, Crianlarich and Oban, bringing ScotRail travel disruption to and from the area.
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