The cost of VMS components will vary according to the functionality requirements of the specific system being implemented. In general the higher the functionality the more expensive the equipment and required data link (airtime costs). The cost of a VMS system therefore varies and thus the level of government subsidy (if any) varies according to national and regional requirements. EU and US VMS systems require expensive onboard equipment and large amounts of data to be transmitted over satellite link resulting in high airtime charges, but also provide a very high level of functionality. In other regions where per vessel cost and huge fleet sizes are an issue, communication technologies such as AIS are used which significantly reduce equipment and airtime costs whilst delivering acceptable basic VMS system functionality.