If aircraft reach a clearance limit before receiving a further  clearance from ATC, a holding pattern is required at the  last assigned altitude. Controllers assign holds for a variety  of reasons, including deteriorating weather or high traffic  volume. Holding might also be required following a missed  approach. Since flying outside the area set aside for a  holding pattern could lead to an encounter with terrain  or other aircraft, aircrews need to understand the size of  the protected airspace that a holding pattern provides.  Each holding pattern has a fix, a direction to hold from  the fix, and an airway, bearing, course, radial, or route on  which the aircraft is to hold. These elements, along with the  direction of the turns, define the holding pattern.  Keep in mind that the maximum speeds specified in 14 CFR  Part 91, § 91.117 still apply during speed adjustments. It is  the pilot’s responsibility to advise ATC if an assigned speed  adjustment would cause an exceedence of these limits.  For operations in Class C or D airspace at or below 2,500  feet above ground level (AGL), within 4 NM of the primary  airport, ATC has the authority to approve a faster speed than  those prescribed in 14 CFR Part 91, § 91.117.  Pilots operating at or above 10,000 feet MSL on an assigned  speed adjustment that is greater than 250 KIAS are expected  to reduce speed to 250 KIAS to comply with 14 CFR Part  91, § 91.117(a) when cleared below 10,000 feet MSL, within  domestic airspace. This speed adjustment is made without  notifying ATC. Pilots are expected to comply with the other  provisions of 14 CFR Part 91, § 91.117 without notifying  ATC. For example, it is normal for faster aircraft to level off  at 10,000 feet MSL while slowing to the 250 KIAS limit that  applies below that altitude, and to level off at 2,500 feet  above airport elevation to slow to the 200 KIAS limit that  applies within the surface limits of Class C or D airspace.  Controllers anticipate this action and plan accordingly.  Since the speed of the aircraft affects the size of a holding  pattern, maximum holding airspeeds have been designated  to limit the amount of airspace that must be protected. The  three airspeed limits are shown in Figure 2-73 in Chapter 2,  En Route Operations, of this book. Some holding patterns  have additional airspeed restrictions to keep faster aircraft  from flying out of the protected area. These are depicted  on charts by using an icon and the limiting airspeed.  DME and IFR-certified GPS equipment offer some additional  options for holding. Rather than being based on time, the  leg lengths for DME/GPS holding patterns are based on  distances in nautical miles. These patterns use the same  entry and holding procedures as conventional holding  patterns. The controller or the instrument approach  procedure chart specifies the length of the outbound leg.  The end of the outbound leg is determined by the DME  Speed restrictions of 250 knots do not apply to aircraft  operating beyond 12 NM from the coastline within the  United States Flight Information Region in offshore Class  E airspace below 10,000 feet MSL. In airspace underlying  a Class B airspace area designated for an airport, pilots are  expected to comply with the 200 KIAS limit specified in 14  CFR Part 91, § 91.117(c). (See 14 CFR Part 91, § 91.117(c)  and 91.703.) Approach clearances cancel any previously  assigned speed adjustment.  Figure 3-18. Instead of flying for a specific time after passing the holding fix, these holding patterns use distances to mark where the  turns are made. The distances come from DME or IFR-certified GPS equipment.  3-21  T SE “...Viking 5786P, hold east of the 20 DME fix on the  265° radial of the stedman VORTAC, 5 mile legs...”  “...Bonanza 8394K, hold  northeast of the 16 DME fix on  the 030° radial of the stedman  VORTAC, 5 mile legs...”  Holding Patterns 