No RER B trains were running between the centre of Paris and Charles de Gaulle airport on Tuesday after a train brought down overhead power cables.
The damage stretched over a full kilometre (0.6 miles), cutting traffic between Paris and the airport, which lies to the north of the capital, said the spokesman for SNCF.
Services were suspended shortly before 9am on Tuesday morning and will not operate again until 6pm at the earliest.
That means there are no RER B trains between Gare du Nord and Charles de Gaulle airport, so air passengers will have to find an alternative way to get to CDG. Trains to Orly Airport, also served by RER B were not affected.
Images posted on Twitter showed passengers having to descend from the trains and walk along the tracks.