Airport Advisory Board, a volunteer board appointed by the Pitkin County Board of County Commissioners to advise them on airport and aviation issues. In practice, it appears to be guided by County staff rather than fully independent.

The Airplane Design Group is an FAA-defined designation of aircraft types, based on wingspan and tail height, that divides planes into six groups. ADG is used to determine which aircraft are approved to operate at each airport. For example, ASE is an ADG III airport with a modification of standard (MOS, see below) that specifies a 320-foot separation between the centerlines of the runway and taxiway, and a County Ordinance that limits the wingspans of acceptable planes to 95 feet rather than the ADG III standard of 118 feet. Otherwise, the standard 400-foot separation would allow bigger planes like the 737-700 and A-320 to land at ASE.

Airport Layout Plan, defined by the FAA as “a critical planning tool that depicts both existing facilities and planned development for an airport.” Public airports are required to maintain a current ALP that has been approved by the FAA. A new ASE Airport Layout Plan, redesigned for bigger planes, was approved by the BOCC in 2024 for submission to the FAA, replacing a 2016 version.

The airport code for Aspen/Pitkin County Airport, sometimes written as KASE.

The Board of County Commissioners is the decision-making board for Pitkin County that establishes, evaluates, and revises codes, policies, and service programs for the county. It has five members with staggered four-year terms. Each Commissioner represents a specific district but is elected by all county voters. Our BOCC has more power than most because Pitkin is one of Colorado’s three Home Rule Counties.

The Federal Aviation Administration is a US government agency within the Department of Transportation that regulates and ensures the safety and efficiency of US civil aviation.

A Fixed-Base Operator is a commercial business or public body given permission to operate at an airport, for a fee, and provide aeronautical services—including fuel, parking, hangar space, aircraft repair and maintenance, customs, and passenger services—to private (non-commercial) planes, their owners, and their passengers. “FBO” can also refer to the operation of private aeronautical services.

A Modification of Standard (sometimes referred to as MOD and pronounced “mod” for short) is an exception granted by the FAA that allows an airport to violate an FAA standard or requirement related to airport design, construction, equipment, etc. in order to achieve lower costs or greater efficiency, or to accommodate an unusual local condition. ASE’s most important MOS reduces the standard runway/taxiway separation (see ADG).

Some people oversimplify this as “widening the runway,” which is a completely separate issue (see “Runway Length and Width” below). “Airfield expansion” is a common shorthand for a new layout to fit bigger planes, but it would not literally mean a bigger airfield. The key ASE controversy is about the separation between the centerlines of the runway and taxiway, so planes passing each other on the ground can’t sideswipe. The FAA designed Aspen’s 95-foot wingspan limit to make the planes now using ASE just as safe with our nonstandard 320-foot runway/taxiway separation as a standard Class III airport would be with its 118-foot-wingspan jets and 400-foot separation.

The length and width of a runway are a function of the size and weight of planes approved to land at an airport. The length of a runway also depends on the local topography, altitude, temperatures, winds, and surface conditions. For example, ASE’s 7,820-foot altitude, its location at the end of a box canyon, nearby peaks with altitudes over 14,000 feet, and unpredictable mountain winds and weather combine to make this specific airport exceptionally challenging, and even unsafe for aircraft with too little power and agility. Width is a different issue. By FAA rule, aircraft weighing over 150,000 pounds must have runways 150 feet wide. ASE’s runway is 100 feet wide and is designed for regular use by planes weighing up to 100,000 pounds—another limit set by County Ordinance.