Understanding dangers associated with winter mountain weather

Better education, familarity and thorough planning contribute to safe flight.

By Julian Tonsmeire
Contributing Writer

Aircraft on the Atlantic Aviation ASE (Aspen CO) ramp on a typical stormy morning. Limited hangar space can be problematic at many mountain airports.

Mountain airport operations can be challenging, especially in winter. While nothing can replace operational experience, proper planning for all phases of flight can reduce workload significantly.

Predeparture planning

This phase should begin as soon as a trip to a mountainous airport is confirmed. Besides the usual pre-trip planning it may be necessary to make slot reservations and recognize the constraints of limited ramp and hangar space once on the ground.

Slots, or in FAA parlance Special Traffic Management Programs (STMP or e-STMP), “are designed to manage unscheduled aircraft operations at airports in close proximity to specific events attracting a significant number of spectators and aircraft,” according to FAA’s ESTMP website.

Details for the coming year can be found at fly.faa.gov/estmp usually by November. The program has become less restrictive in recent years with fewer dates and fewer airports. Traditionally, the program only applies to the most popular mountain airports such as ASE (Aspen CO), EGE (Eagle CO), JAC (Jackson Hole WY), RIL (Rifle CO), SUN (Hailey ID), TEX (Telluride CO) and TWF (Twin Falls ID) surrounding peak travel dates—Christmas, New Year and Presidents Day weekend.

Slot reservations can only be made online and are available exactly 72 hours prior to the requested arrival time. It’s always wise to list an alternate, so even if you don’t get your first choice—say, ASE—you might get a close alternate such as EGE or RIL.

Be sure to communicate to your passengers that the FAA slot reservation system is a lottery involving some randomness. In past years, when operators did not get their requested slots—or ended up with an alternate airport slot—FAA sometimes released additional slots based on a favorable weather forecast and canceled slots the afternoon before at a specific time.

Slot confirmation 24 hours out has helped reduce unused slots and created an additional opportunity to get your preferred time and destination. Finally, it is important to mention the need to cancel any slot you don’t intend to use.

This ensures all operators have the best possible chance of getting a slot. Finding transient hangar space or even a sliver of ramp to occupy at certain mountain airports can be difficult at peak times. “When making FBO arrangements it’s never too early to call,” says Atlantic Aviation ASE Customer Service Mgr Amy Dengler.

If you must hangar, be prepared to reposition 100 miles or more. In addition, crew hotels can be difficult to acquire, so plan as far ahead as possible. Many flight departments have operational limitations in their ops manual specific to mountain airports, so be sure to review these policies.

Does your flight department have higher-than-published approach minimums or weather requirements for specific mountain airports, or should they? Also, consider carefully your flightcrew’s airport familiarization, specific ap­proach training (including ap­proach-specific simulator or recent experience with approach procedures), and the conditions you may face—IMC, night, etc.

Consider what kind of weather you are willing to operate in, such as icing, night or circling ap­proaches. “Advance planning is key to coming into mountain airports in the winter,” says Todd Chilton, a Learjet 60 pilot and former ops dir for an RIL-based Part 135 operator.

Again, it is essential that all operational limitations be communicated effectively to passengers well in advance to deliver the safest customer focused service possible.


Once airborne and in­bound to mountain airports, keep an eye on the weather via on board satellite-weather or an enroute flight advisory service (or flight watch). Mountain valleys tend to have weather that changes by the minute.

Bill Landis, an ASE-based Citation 560 pilot and former Aspen Aviation dir ops, says, “In­bound on a long flight I’m really monitoring trends and trying to get an idea if it’s improving or deteriorating, so when I arrive I know if it’s worth trying the approach, holding and waiting for a break, or just diverting.”

When checking weather enroute, pay especially close attention to braking action. In general, braking action will improve with rising temperatures—like in the morning—and deteriorate with decreasing temperatures. “If there’s any chance of weather at the mountain airport I’m headed to, I tell the passengers there’s a 50/50 chance we’ll get in,” says Bill Gibson, a long-time ASE/EGE/RIL-based pilot who flies a G550, Falcon 2000 and Citation 550.

It is important to create realistic expectations for passengers both prior to departure and enroute, given that mountain weather changes rapidly and can be extremely localized. Landis points out, “The way the topography works in the central Colorado Rockies, when the weather in EGE is down, ASE or RIL tend to be up, although these airports are only 20–30 miles apart.”

If weather is looking marginal, a decision will have to be made to put ground transportation in place at your alternate airport. During peak season, rental cars or limos may be difficult to come by. Common alternate airports such as RIL and TWF have excellent ground transportation options, but plans must be in place prior to departure.

Having the foresight to place a car at your alternate is sure to impress passengers as other aircraft passengers wait hours for ground transport to arrive.


Mountain airports present challenging and often complicated approach procedures. Many simulator training providers such as CAE and FlightSafety Intl provide specialized mountain airport training or can build it into the usual initial or recurrent aircraft training.

Recently improved arrival end of Runway 9 at TEX (Telluride CO).

Also, if you frequent specific mountain airports you may want to consider FAA’s Special Instrument Procedure Authorization process. This can gain your operation access to additional approach and departure procedures not available without specific training, currency and FAA approval. “It can be a real eye opener to fly instrument procedures on a VFR day into mountain airports and see what you’re up against,” notes Gibson.

Solid instrument conditions near minimums may not be the best time to fly an unfamiliar complicated instrument procedure in unforgiving terrain. Throw in night and icing conditions and you have a recipe that has led to many accidents.



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