The golden question: Why do this to us? Again!
In short, it's all about workers getting rail network SNCF to improve pay and working conditions. The strike, as they often are in France, is about rail workers flexing their muscles to try and influence negotiations between unions and bosses.
But the negotiations are significant because of what is at stake.
SNCF is preparing for the world of competition that's being forced on them by the European Union. The French rail service will be opened up to competition in stages over the coming years, firstly freight traffic, which has already occurred, then passenger services like the TGVs from 2020. SNCF wants to be ready.
The operator wants to harmonize the working conditions and rules between SNCF workers paid by the state and rail workers who work for private companies.
Unions claim it will lead to "social dumping" and leave everyone worse off.
It's a very sensitive issue in France, where rail workers are often criticized for being too privileged. These workers, backed by powerful unions like the CGT, are obviously keen not to lose their perks and conditions. They fear the changes will simply lead to more working hours and fewer days off and all in all worse conditions.
While SNCF believes it's time for them to become more competitive, unions believe the private competitors should improve their workers conditions to meet the standards set by SNCF.
While SNCF has vowed not to touch the main privileges, like social security, protection from lay-offs, and pensions, rail bosses are focused on two changes - changing working times to adapt better to the 35-hour working week, and making staff more flexible and available to do more varied tasks.
For example, the system today sees a train conductor getting the next day off if they finish their shift after 7pm. SNCF wants to bring an end to this.
SNCF also wants to diversify the workload, meaning a ticket collector at a station could potentially end up doing shifts on an actual train, or even working on the infrastructure itself.
Workers are worried this means they could lose out, considering that what today takes maybe three or four people could be done by one.
Roger Dillenseger of the Unsa union said the new plans aren't efficient and disregard workers' rights. He criticised one ofthe planned changes that could see rail workers finish their shift anywhere within a 50 km radius of where they live, and then have to find a way home.
Other bones of contention lie around how many weekends SNCF workers have off each year and a plan to make night shifts last eight hours rather than seven.
Rail unions appear to be in a powerful position, hence their threat to continue strike action if they don't get what they want.
They've held a national demonstration on May 10th (without any stoppages on the rails) which attracted 15,000 people, according to the CGT union.
The last thing the French government wants is another long-running social movement, given the ongoing protests against unpopular labour laws. Especially not with next year's presidential elections on the horizon.
There is also the small matter of the Euro 2016 football championships from June 10th to July 10th where fans will need train services to get around. The thought of a strike crippling rail travel during the tournament will have the French government in a sweat.
But it's a distinct possibility given that French unions have already threatened to flex their muscles again during the tournament.
Strikes in late April, which were backed by all four trade unions (UNSA, CGT, SUD, CFDT) saw a day of travel chaos with half of the nations TGV services running, and delays on the RER and TER lines.
What should I do during a strike?
There will usually be replacement staff on hand at rush hours to ease congestion, but passengers are being advised to delay all non urgent travel.