Coal India (CIL) recently found out that as many as four trade unions are planning to strike from January 6th ? 10th. India is currently facing large coal shortages, so a strike could pose a major threat. The unions have already threatened to go on strike once this month but did not carry out their plans. The CIL has received no official notice that there will be strikes in January.
See "Coal India Ready for Conciliation as Unions Threaten to Strike", The Economic Times, December 22, 2014