Source: http://www.outsideonline.com/adventure-t...

The bad news first. Airlines aren't bound to their schedules. They promise to get you from point A to point B, but make no guarantees about timeline. You blew a lucrative business deal because of a cancelled flight? Good luck getting any airline to pay you damages. Airlines set their own policies about what they'll offer delayed passengers—there's no federal guideline dictating a consistent course of action. 

In fact, the only time airlines are required to compensate inconvenienced customers is when they're bumped from an oversold flight. In that case, all the airlines should offer pretty much the same deal: They'll put you on their next available flight. If you reach your destination one to two hours later than originally scheduled, they'll pay you 200 percent of the one-way fare (up to $650). More than two hours later, and you're entitled to 400 percent (up to $1,300).

The problem? Most travelers don't receive the full amount they're entitled to, according to AirHelp, a new app that offers to collect unpaid compensation from the airlines. Last year, involuntarily bumped passengers received $391 to $439 each, but AirHelp estimates those payouts should've averaged $643.60. Check your airline's offer against the rules. 

If you're bumped, some airlines (United is one) will book travelers on another carrier if you request it; others (such as Delta) will do it at their discretion, not yours. Still others (including Southwest and Spirit) don't have any agreements with competing airlines, so their planes are your only options.