AIM 

6/17/21 

b. 

The FAA has identified three possible situations 

where the failure to plan for an alternate airport when 
flying IFR to such a destination airport could result in 
a critical situation if the weather is less than forecast 
and sufficient fuel is not available to proceed to a 
suitable airport. 

1. 

An IFR flight to an airport where the 

Minimum Descent Altitudes (MDAs) or landing 
visibility minimums for 

all instrument approaches 

are higher than the forecast weather minimums 
specified in 14 CFR Section 91.167(b). For example, 
there are 3 high altitude airports in the U.S. with 
approved instrument approach procedures where all 
of the MDAs are greater than 2,000 feet and/or the 
landing visibility minimums are greater than 3 miles 
(Bishop, California; South Lake Tahoe, California; 
and Aspen

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Pitkin Co./Sardy Field, Colorado). In the 

case of these airports, it is possible for a pilot to elect, 
on the basis of forecasts, not to carry sufficient fuel to 
get to an alternate when the ceiling and/or visibility 
is actually lower than that necessary to complete the 
approach. 

2. 

A small number of other airports in 

mountainous terrain have MDAs which are slightly 
(100 to 300 feet) below 2,000 feet AGL. In situations 
where there is an option as to whether to plan for an 
alternate, pilots should bear in mind that just a slight 
worsening of the weather conditions from those 
forecast could place the airport below the published 
IFR landing minimums. 

3. 

An IFR flight to an airport which requires 

special equipment; i.e., DME, glide slope, etc., in 
order to make the available approaches to the lowest 
minimums. Pilots should be aware that all other 
minimums on the approach charts may require 
weather conditions better than those specified in 
14 CFR Section 91.167(b). An inflight equipment 
malfunction could result in the inability to comply 
with the published approach procedures or, again, in 
the position of having the airport below the published 
IFR landing minimums for all remaining instrument 
approach alternatives. 

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11.  Flights Outside U.S. Territorial 

Airspace 

a. 

When conducting flights, particularly extended 

flights, outside the U.S. and its territories, full 
account should be taken of the amount and quality of 
air navigation services available in the airspace to be 

traversed. Every effort should be made to secure 
information on the location and range of navigational 
aids, availability of communications and meteoro-
logical services, the provision of air traffic services, 
including alerting service, and the existence of search 
and rescue services. 

b. 

Pilots should remember that there is a need to 

continuously guard the VHF emergency frequency 
121.5 MHz when on long over-water flights, except 
when communications on other VHF channels, 
equipment limitations, or cockpit duties prevent 
simultaneous guarding of two channels. Guarding of 
121.5 MHz is particularly critical when operating in 
proximity to Flight Information Region (FIR) 
boundaries, for example, operations on Route R220 
between Anchorage and Tokyo, since it serves to 
facilitate communications with regard to aircraft 
which may experience in-flight emergencies, com-
munications, or navigational difficulties. 

REFERENCE

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ICAO Annex 10, Vol II, Paras 5.2.2.1.1.1 and 5.2.2.1.1.2. 

c. 

The filing of a flight plan, always good practice, 

takes on added significance for extended flights 
outside U.S. airspace and is, in fact, usually required 
by the laws of the countries being visited or 
overflown. It is also particularly important in the case 
of such flights that pilots leave a complete itinerary 
and schedule of the flight with someone directly 
concerned and keep that person advised of the flight’s 
progress. If serious doubt arises as to the safety of the 
flight, that person should first contact the appropriate 
FSS. Round Robin Flight Plans to Canada and 
Mexico are not accepted. 

d. 

All pilots should review the foreign airspace 

and entry restrictions published in the appropriate 
Aeronautical Information Publication (AIP) during 
the flight planning process. Foreign airspace 
penetration without official authorization can involve 
both danger to the aircraft and the imposition of 
severe penalties and inconvenience to both passen-
gers and crew. A flight plan on file with ATC 
authorities does not necessarily constitute the prior 
permission required by certain other authorities. The 
possibility of fatal consequences cannot be ignored in 
some areas of the world. 

e. 

Current NOTAMs for foreign locations must al-

so be reviewed. International Notices regarding 
specific countries may be obtained through the Feder-
al NOTAM System (FNS) NOTAM Search External 
Links or the Air Traffic Plans and Publications web-

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Preflight