The remainder of the build is the control tower and terminal building. First there is a metal detector screener leading to the waiting/secure area of the airport, which seems taller than it needs to be for the minifigures. I think the same effect could have been made with half the height, except that would not allow for an impressive height for the overall tower. However it does seem to be similar to many modern airports with the high ceilings. This area also seems to be someplace to check luggage as evidenced by the rather nifty conveyor belt that comes in a full part. The moving parts of the set include a revolving door (a very tall one, for the first floor) that leads from the secure area of the airport out to the tarmac, and of course the conveyor belt. 

Correct me if I'm wrong, but is the hangar only large enough to house the biplane? A bit of a cock-up if that's the case. As good as the planes are, the hangar is a major failing. It looks like it's only about 30-40 pieces; just a bunch of big plates, some prefab cross-bracing and ... errrm ... air. Not so much a "hangar" as an aviation-equivalent of a car port!
Bag 6 starts the airport terminal.  Like most CITY builds, they are meant for play so it's really only half a building.  It includes one minifigure and the revolving door entrance.  While the entrance is cool looking, it's about twice the height of a minifigure and there isn't enough physical space for one actually to fit through the door.  I'm not a fan of the design.
City is the thematic title under which most Town-related System sets were released from 2005 and onward. There are numerous sets that are associated with Construction, Police, Fire, Emergency, Train, Airport, Transportation, Cargo, Traffic, Coast Guard, Farm, Great Vehicles, Mining, and Space. European catalogs featured another theme called City in the years 1999 to 2000, which was referred to as City Center in American catalogs.

Correct - the hanger can only accommodate the biplane. That having been said, in order to accommodate the other aircraft too the hangar would have to be huge, with an enormous footprint, and a substantially increased parts count. As a result, I'd estimate a price up to double the current RRP which I suspect few of the target market would pay. LEGO therefore got the size of the hanger right IMHO.
I did prefer the previous 3182 airport set as it had a lot more components. But, I realise that it makes more business sense to offer a little less than raise the price of an already expensive product. However, 60104 is still a nice set and is often very well discounted in the UK so, I ordered a pallet load from Tesco during their 3-for-2 which made them a half-priced no-brainer ;-)
Billund Airport had its beginning in 1961 when the son of the founder of the Lego Group, Godtfred Kirk Christiansen, established a private 800-meter long runway and hangar north of his factory in Billund. With Christiansen as a key driver, more of the neighbouring municipalities were included in the group of owners, and it was planned that the airport should be expanded to a regular public airport.