Contracts are given to you by various companies, and allow you to obtain fuel, hire contractors, and accept commercial aircraft.
Fuel contracts allow automatic on-demand fuel deliveries to the airport. There is an initial fee upon accepting the contract, and a price per liter of fuel delivered - both of which will vary based on the contract. After accepting the contract, fuel will be delivered when a fuel depot depletes past a certain percentage of capacity (stipulated on the contract).
Signing a contract with a construction company allows you to call in contractors. Contractors are necessary for any sort of construction. There is an initial fee upon accepting the contract, a fee for every time the contractors are called in, a wage per hour for the service of the contractors, and the number of contractors available - all of which will vary based on the contract. After accepting the contract, you will be able to call the contractors in by going to Operations, selecting the Construction tab, and pressing the green "Call Contractors" button. It is possible to manually adjust the number of contractors being deployed as is the number of contractors being dismissed. Dismissing contractors upon completion of work will reduce unnecessary contractor fees, as contractors continue to be paid as long as they are in service.
Contractors require a Contractor Off-load site with road access to be present at your airport, and a Delivery site with road access is required for their construction materials to be delivered. Both of these can be placed directly, without the construction process.
An airline contract is necessary to start accepting flights from airline companies. Each contract comes with a series of tasks that must be completed in order to complete the contract, a deadline to complete the contract, and a payment received per flight. Completing the details on the contract in the time limit will award a cash bonus, if stipulated in the contract.
A catering contract allows you to make food for passengers that can then be put on the plane. The contract will bring you food to be made into meals.
De-Icing Fluid Contracts
This contract allows you to get De-icing fluid from a contract to be used to de ice large and medium planes.