AirTran, JetBlue, Southwest Airlines and Sun Country Airlines are generally referred to as low-cost airlines

Why might this type of industry be used as an example of a contestable market? Can you think of any reasons why this might not be a good example of a contestable market?

Entrants have the possibility of leasing aircraft and should be able to respond to high profits by quickly entering and exiting. There may be entry/exit barriers in the form of terminal leases, availability and predatory pricing by incumbents, signaled through built-in overcapacity which may make this a weak example of a contestable market.