as an air traffic controller in Chicago I can tell you that the airlines do thier best to get you to your destination. the weather was bad they could not get to MSP before they ran out of gas, and they went to thier alternative airport. We try to best the we can to get them in, ask thier last minute to diverete, and if we can we squeeze them in ahead of a plane that has been waiting longer, but sometimes due to weather we just can't get you in and you end up diverting