The fuel advantages of the CFM-56-7 are so good, that they outweigh things like staffing, etc. Also, there is a lot less MX
expense on the 738s, as well as no need to dedicate planes to certain routes, FR
can fly any plane at any time.
>They are starting to replace some of them with the 737-800, but will they only buy 737-800s or will they buy annother other aircraft like the A319/A320?<
They have over 200 737s in the fleet or on order, with more on option. They are not buying anything other that the 737. Also, when you consider the things Mike O'Leary has said about Airbus and EADS, I don't think they will be talking anytime soon. They did talk to Airbus about switching to an A320 fleet back when they made their second (there have been three, the second being the biggest) order for the 738. They used that as leverage to get a better price for the 738 and Boeing was more than happy to oblidge. They are now one of Boeing's flagship carriers and will not be ordering anything else for some time. The only airline less likely to fly A320s that FR