Airlines reserve the right to postpone or cancel any flight without prior notice.

The first announcement may be that there will be a delay of only 15 or 20 minutes, but this may drag into hours.  If bad weather or air traffic congestion is the cause, it probably affects all airline operations.

If the delay is due to mechanical problems, lack of equipment, lack of crew, however, you may save time by insisting that he airline get you on another carrier (whether or not they have a "co-share" provider).  If you elect this optional course of action, be sure the airline with the delay will absorb any cost difference before you accept alternate arrangements.

If the flight is cancelled, most airlines arranged alternate transportation on the next available flight to your destination.  This "involuntary rerouting" and there is not additional charge, even if you are upgraded to First Class.  A" no frills" airline may offer you a choice of seats on their next flight or a refund.  This may also happen if you are traveling on a discounted fare.

There is an industry rule for dealing with cancellations or delays – Rule 240.  It is basically says the airline is obligated to provide alternate transportation on another of it's flights, through rerouting, or even on another airline – at not additional cost. But, the passenger has to ask that this be done.  If the airline refuses, ask to see its Terms and Conditions of Carriage to prove it has not obligation.

In the past, airlines automatically provided meals, lodging, and phone calls for passengers facing long delays or cancellations.  This was not a requirement, however, and few make this offer (in whole or in part), today, unless a flight as diverted to an unexpected airport.

Some airlines do give their personnel latitude in providing these amenities to insistent passengers.  You may get them if you are assertive (but not confrontational!), but the airline has not obligation to provide them!