Visibility and cloud clearances for operations conducted in  Class E airspace are similar to those of the Class G airspace.  If balloon operations are being conducted below 10,000 feet  MSL, visibility is three statute miles and the basic VFR cloud  clearance requirements of 1,000 feet above, 500 feet below,  and 2,000 feet horizontal (remember the C152 mnemonic).  Operations above 10,000 feet MSL require visibility of five  statute miles and cloud clearance of 1,000 feet above, 1,000  feet below, and one statute mile horizontally. Class D is that airspace from the surface to 2,500 feet AGL  (but charted in MSL) surrounding those airports that have  an operational control tower.  [Figures 5-2  and 5-5] The  configuration of each Class D airspace area is individually  tailored. When instrument procedures are published, the  airspace is normally designed to contain the procedures.  Class C airspace normally extends from the surface to 4,000  feet above the airport elevation surrounding those airports  having an operational control tower, that are serviced by a  radar approach control, and with a certain number of IFR or  passenger operations.  [Figures 5-2  and  5-6]  This airspace  is charted in feet MSL, and is generally of a five NM radius  surface area that extends from the surface to 4,000 feet above  the airport elevation, and a 10 NM radius area that extends  from 1,200 feet to 4,000 feet above the airport elevation.  There is also a noncharted outer area with a 20 NM radius,  which extends from the surface to 4,000 feet above the  primary airport, and this area may include one or more  satellite airports.  [Figure 5-7] of Federal Regulations (14 CFR) part 91, section 91.113, a  pilot would cause less disruption by landing well short of  the airport. This is nothing more than common courtesy  and common sense. The visibility requirement for Class  D airspace is three statute miles; cloud clearances are the  standard VFR 1,000/500/2,000. Class C Airspace Class D Airspace Unless otherwise authorized, each aircraft must establish  two-way radio communications with the ATC facility  providing air traffic services prior to entering the airspace  and thereafter maintain those communications while in the  airspace. Balloon pilots approaching Class D airspace should  call the ATC facility at a point where, if entry is denied, a safe  landing can still be executed. It is important to understand  that if the controller responds to the initial radio call without  using the balloon’s call sign, radio communications have not  been established, and the balloon may not enter the Class D  airspace. Many airports associated with Class D airspace do  not operate on a 24-hour-a-day basis. When not in operation,  the airspace will normally revert to Class E or G airspace,  with no communications requirements. In either case, balloon  pilots are reminded that, in the absence of an emergency  situation, there is no absolute requirement to land at the  airport associated with the Class D airspace. In most cases,  the first radio call will be made at a distance of five statute  miles from the airport.  Balloon pilots operating in the vicinity of an airport should  exercise discretion. While balloons indeed have the right of  way over all powered aircraft as stated in Title 14 of the Code  Figure 5-7.  Example of Class C airspace on a sectional. 5-4 Figure 5-6.  Class C airspace. Figure 5-5.  Class D airspace. Class C Entry Requirements Minimum Pilot Qualifications Two-Way Radio Communications VFR Visibility Minimum VFR Minimum Distance from Clouds Prior two-way communications Student certificate Yes 3 statute miles 500' below,1,000' above,  2,000' horizontal Class D Entry Requirements Minimum Pilot Qualifications Two-Way Radio Communications VFR Visibility Minimum VFR Minimum Distance from Clouds Prior two-way communications Student certificate Yes 3 statute miles 500' below,1,000' above,  2,000' horizontal