What Happens If Something Goes Wrong?
Ultra Low Cost Airlines:
In the event your flight is canceled or delayed, the airline will usually make you wait out the delay, or offer you a refund of your ticket price. Unlike legacy carriers that have spare aircraft ready for such occasions, ultra low cost airlines keep all of their planes flying to make money and keep ticket prices low. They do not maintain agreements with other airlines to re-book passengers, so in the event of bad weather, mechanical problems, or some other type of issue, your options are very limited.
If the idea of missing your vacation due to a problem with a plane worries you, then consider booking with a legacy airline as a type of insurance policy. In the event your flight is canceled, delayed, overbooked, or you miss a connection, they will accommodate you on another flight of theirs, or place you on a competitor airline that they have an agreement with.
Here is a basic example:
You are flying on the once daily Spirit Airlines flight from Pittsburgh to Las Vegas in order to save money. You get to the airport and find out the flight was canceled due to mechanical reasons. Due to the popularity of the flight, they can’t re-book you on another flight until 2 days later. You can accept this offer or a refund from the airline.
In the same scenario, you are flying on United Airlines from Pittsburgh to Las Vegas. You arrive at the airport and find out the flight has been canceled due to mechanical reasons. The airline has already booked or will book you on a new flight connecting you through another hub of theirs (New York, Chicago, San Francisco, Washington D.C.). Sometimes you luck out and arrive around the same time or earlier, and other times you arrive a bit later, but you ultimately end up at your destination without much of a delay.