Aircraft leases are also regulated by the FAA in the Federal Aviation Regulations (FARs). The FAA classifies aircraft leases as either "dry leases" of "wet leases". Under a dry lease, the aircraft owner provides only the aircraft and no crew. If at least one crew member is provided in the lease arrangement, this becomes a wet lease as defined in the FARs. A wet lease is an exception to the simple definition of a lease because it does not involve transferring possession of the aircraft. The lessor maintains operational control of the aircraft under a wet lease. Without a specific exemption, such as a time sharing agreement, or other options found under FAR 91.501, a wet lease requires an FAA commercial operating certificate.