Correct. The firm, in this Continental, main goal is to maximize revenue. If they sold seats at lower prices shortly before a flight departs, yes they would sell some previously unsold seats, but would lose out, potenitally, on customers who purchase high fares in advance.

If Continental would make more money selling seats at a discount, lets say, 24hrs before departure, they would. Its the same thing with movie tickets. If movie theaters sold tickets 5 minutes after a show began for $.50, that would be extra $ for them. The problem is people would stop paying $10 normally and try to get the $.50 ticket.