Return to the hangar, where the count is already waiting for you. Talk to Sara to finalize the airship purchase. You will learn that the ship has to be filled with has to be filled with gas and you're out of hydrogen, you'll need to produce it. Sylvie will have to, not too legally, connect to an electricity source.
Go to the boxes on the left and take the cable. Connect one end to the electricity box by the hangar and the other to the box by the entrance gate. Afterwards go into the hangar.
Inside, Take a look below the platform by the stairs (zoom) and take the oil container. Check the locker (zoom). Take the empty oiler from the upper right shelf and a rack from the left one.
Now go to the crates on the left of the airship (zoom), pick up the chain lying on the ground (between the planks on the right) and a link by the crate on the left.
Go up the stairs onto the platform. Take a look at the green mechanism (zoom). Put the chain into the proper place (on the left) and add the missing link. Inside the mechanism, put the rack between the two that are already there. Fill up the oiler in the inventory. Oil the whole mechanism and turn the crank on the right.
Afterwards go to the end of the platform to the gas generator (zoom). Take the shovel standing on the right and take some salt from pile in front. Try to press the switch on the left. The device won't work, so go to Sara to learn that you need a valve which has been ordered and is waiting in a package in the customs office. The woman will give Sylvie a wad of banknotes, with which you should head to the police station and talk with the man in the customs section. After a while you will receive the package. Unpack it (click it in zoom) to get the valve.
Return to the hangar and onto the platform. This time turn left (to the pump) right before the generator. Put in the valve in the empty spot between the pipes. Return to the generator and press the button (on the left). Go outside to say goodbye to Sylvie and after a while you'll be in the airship with the count.