The Mining and Energy Union said Friday it secured a retention bonus for all rail crew members in the bargaining period with BHP Group (ASX:BHP) for the current rail crew agreement.

In addition, Rio Tinto Group (ASX:RIO) amended its policy on flight delays for "fly-in fly-out" workers traveling home, compensating them for flights delayed over four hours with AU$500 and over 12 hours with AU$1000, the union said in a statement.

The Western Mine Workers Alliance had asked the mining firm to compensate workers whose flights were delayed on the way home with AU$100 per hour of delay.

Rio Tinto and BHP Group's shares were each down 1% in recent Friday trade.