I want to use a lower boundary for a positive variable (holdtime(i,w1,w2)) iff the flight (i) requires it.
If I use holdtime.lo(i,w1,w2)>=50, the model gives 50 secs to all flights(i). But, I just want iff the flight requires holdtime going from w1 to w2., then it can get at least 50 secs.
I have just solved, but still wondering if any more sophisticated solution. I have just added three constraints with a new binary variable;
It makes holdtime either 0 or greater than 50 secs.