Explainer02 OCT 20267 min readDromopedia editors

Hard, not dangerous

The same dozen airports head every list of the world's most dangerous. Aviation authorities keep lists too. Theirs name the terrain, and require that the captain has seen the airport before.

KASE RWY33
Aspen-Pitkin County Airport (Sardy Field) · Avitya · Public domain · Commons

Search for the world's most dangerous airports and the same names come back: Lukla, Paro, Courchevel, Saba, Saint-Barthélemy, Madeira, Toncontín, Innsbruck, Aspen, Gibraltar.1 The lists seldom say how the danger was measured, and counting accidents does not reproduce them. The register's timelines hold 951 accidents at 623 airports, all taken from Wikidata. The airports with the most are Sheremetyevo with ten, Vnukovo with nine, and Irkutsk, Almaty and LaGuardia with eight each.2 Those are busy airports with long histories, and the register has no count of flights to divide the accidents by.

What can be pinned down is why an airport is hard. Aviation authorities write that into their rules, airport by airport, and part of it can be measured from a map.

The captain has been there before

United States rules let the FAA declare an airport "special" because of "surrounding terrain, obstructions, or complex approach or departure procedures". An airline may then send a captain there only if, within the past twelve months, the captain or the first officer has landed and taken off at that airport, or the captain has qualified with pictorial material the FAA accepts. In good weather the rule does not apply.3

The FAA's list, in its May 2017 revision, names 93 airports, about two-thirds of them in the United States, and adds blanket entries for most airports in China and the former Soviet Union. For 80 of the 93 the reason given is "mountainous terrain", and 73 entries date from 20 June 1990. Aspen's is fuller: "Mountainous terrain in immediate vicinity of airport, all quadrants; high climb gradient performance requirements; special procedures." Kathmandu was added in 2015 for "steep approach and departure gradients" and a simulator requirement set by Nepal. The list covers the places a US airline might fly to, so Lukla, Paro and Courchevel are not on it.4

European rules name no airports at all. Each airline sorts the aerodromes it uses into categories A, B and C, and lists the B and C ones in its operations manual. Category A needs an instrument approach, a runway without performance limits, circling minima no higher than 1,000 ft and the ability to operate at night. Category B is anything short of that, or anything with unusual weather, approach patterns or "performance limitations". Category C is harder still: before flying there the captain "should be briefed and visit the aerodrome as an observer and/or undertake instruction in a suitable FSTD", a flight simulator.5

Some states write the requirement into their own aeronautical publications. Those entries are the plainest descriptions of a hard airport there are.

Terrain

How much ground stands around an airfield can be measured. For this piece we sampled open elevation data in a circle of 10 km around each airport and took the highest ground above the airfield's own elevation.6 At Heathrow the answer is 59 m, and at Denver 57 m.

PBHParo International Airport BT · 2,245 M / 7,364 FT · RWY 2,265 M / 7,431 FTGround 1,820 m above the runway within 10 km. Daylight and visual conditions only.

At Paro, in Bhutan, it is about 1,820 m. The runway is 2,265 m long and lies at 2,244 m. The 2018 edition of Bhutan's AIP permits flights only by day and in visual conditions, "due to high terrain and steep mountains adjacent to the aerodrome". It warns that the final approach to both runways is curved "due to hilly terrain", that there is no ILS and no visual glide-slope guidance, that severe turbulence may be met on entering the valley, and that only one aircraft at a time may descend in it. Before operating there the pilot in command "should be briefed and visit the aerodrome as an observer", or train in an approved simulator, or ask for a guide pilot.7

The popular lists surround Paro with 18,000 ft peaks. Within 10 km the highest ground is about 4,050 m, or 13,300 ft. Ground near 18,000 ft first appears about 30 km to the north. Eighteen thousand feet is the altitude to which the AIP has departing aircraft climb.6

INNInnsbruck Airport AT · 581 M / 1,907 FT · RWY 2,000 M / 6,562 FTThe ridge 5 km to the north stands 1,940 m above the runway.

Innsbruck has a 2,000 m runway at 581 m on the floor of the Inn valley, and ground 1,940 m higher only 5 km away. The Austrian AIP says that, "due to mountainous terrain in the vicinity of the aerodrome and the requirement for visual manoeuvring", pilots must be well familiar with the procedures, and it makes familiarisation with briefing material mandatory. A crew must have flown there in visual conditions, or in a simulator, before it first uses the instrument approaches in weather below a 3,000 ft ceiling and 5 km visibility. During foehn, a wind from the south-east or south gusting to 30–50 kt, pilots should "expect severe turbulence associated with horizontal windshears and severe downdraughts at all altitudes".8

ASEAspen-Pitkin County Airport (Sardy Field) US · 7,838 FT / 2,389 M · RWY 8,006 FT / 2,440 MOn the FAA's list since 1990. Ground 1,270 m above the runway within 10 km.

Aspen's runway is 2,440 m (8,006 ft) long at 2,389 m (7,838 ft), and its two thresholds differ in height by 48 m, a slope of 2%. The ground within 10 km rises 1,270 m above it.26

A short runway

SABJuancho E. Yrausquin Airport BQ · 18 M / 60 FT · RWY 400 M / 1,312 FT401 × 18 m of concrete, 37.5 m above the sea. Visual conditions only.

The shortest paved runway with airline service in the register is on Saba, in the Dutch Caribbean: 400 m.2 The AIP gives 401 × 18 m of concrete and limits the airport to visual flight. It "is only available to fixed wing aeroplanes with authorisation from Dutch government that have met the airport qualification requirements", and it "is not open to the public".9 The island's summit is 2.25 km from the runway and about 800 m above it.6

SBHSt. Jean Airport BL · 15 M / 49 FT · RWY 646 M / 2,119 FT646 m, sloping down to sea level. Departure on runway 28 is prohibited.

Saint-Barthélemy's runway is 646 m long and 18 m wide, and drops 13 m from one threshold to the other.2 The FAA added it to the list in 2006 with a long entry: "Severe mountainous terrain hindering an approach to both Runway 10 and Runway 28. Departure on 28 is prohibited. French Civil Aviation Authority requires a special flight check from an authorized individual and a signoff to all crewmembers that fly commercially into this airport."4 The 10 km measure barely notices the island: its highest ground is 200 m above the runway. The hills here are low, but they stand at the runway's ends, and a circle of 10 km cannot show that.

Lukla and Courchevel are short too, and steep. They are the subject of Uphill landings.

Wind

FNCCristiano Ronaldo International Airport PT · 59 M / 192 FT · RWY 2,777 M / 9,110 FTMandatory wind limits. Captains requalify every six months.

Madeira's runway is long, and the difficulty comes from the air. The Portuguese AIP describes the site: "The Airport is located on a plateau on the east coast of Madeira Island. Except for the seaside, ground raises rapidly very closed to it. This fact generates, very often, wind variation and turbulence." Severe low-altitude wind shear and microbursts "are likely to be encountered". Within 10 km the ground rises 1,280 m above the runway.6

So the AIP sets wind limits and makes them mandatory. With the wind from between north-west and north, an aircraft may land only if the two-minute mean at the touchdown anemometer is 15 kt or less and gusts are no more than 25 kt. For revenue flights by aircraft with more than ten passenger seats, the captain needs 200 hours in command on the type before completing initial training for Madeira. To stay qualified, the captain must have made a landing and a take-off there in the last six months, or flown both runways in a simulator in simulated bad weather, or made a line training flight with an instructor in the right-hand seat.10

Moving the airport

TGUToncontín Airport HN · 1,004 M / 3,294 FT · RWY 1,863 M / 6,112 FTRunway 1,863 m at 1,004 m. On the FAA's list since 1990.

Hard airports do have accidents. The register's timelines record one at Madeira, in 1977, one each at Aspen and Saint-Barthélemy in 2001, and two at Lukla. Toncontín, the airport of the Honduran capital Tegucigalpa, has three, in 1989, 2008 and 2011.2 Its runway is 1,863 m long at an elevation of 1,004 m. The ground within 10 km rises 710 m above it, and on the approach to runway 02, 2.5 km before the threshold, it already stands about 170 m higher than the runway.6

Honduras moved its capital's international flights. Palmerola International Airport opened at Comayagua in December 2021, and Toncontín was limited to domestic services.11

XPLPalmerola International Airport HN · 628 M / 2,061 FT · RWY 2,458 M / 8,064 FTOpened in 2021. Added to the FAA's list in September 2022.

Palmerola's runway is 2,458 m long at 628 m, and along its centreline the ground stays level with the thresholds for 10 km in either direction. The ground around it is another matter: within 10 km it rises 1,010 m, more than at Toncontín.6 In September 2022 the FAA added Comayagua to its list, "due to mountainous terrain and approach/departure complexities".12 The new airport is easier by every figure here except one, and its captains still have to qualify.

Sources

  1. For example Simple Flying, "The Hardest Airports In The World To Land At"; AeroCorner, "Most Dangerous Airports: 12 Hardest to Land At"; WorldAtlas, "The Most Dangerous Airports in the World". The first two describe Paro as surrounded by peaks of 18,000 ft.

  2. Dromopedia register. Accidents are the events of that kind in the airport timelines, taken from Wikidata: 951 at 623 airports; a count of what Wikidata records, not of all accidents. Toncontín: Tan-Sahsa Flight 414 (1989), TACA Flight 390 (2008), Central American Airways Flight 731 (2011). Runway lengths and elevations: Paro, Innsbruck, Saba, Saint-Barthélemy, threshold elevations 14.6 m and 1.2 m, Toncontín and Palmerola from OurAirports; Aspen, threshold elevations 2,341 m and 2,389 m, from the FAA. Shortest paved runway with airline service: Shortest runways with airline service. The register gives Saba's elevation as 18 m against 37.5 m in the AIP, and Palmerola's opening as 15 October 2021, from Wikidata. 2 3 4 5

  3. 14 CFR § 121.445, Pilot in command airport qualification: special areas and airports, as amended 18 June 2024. Paragraph (c): the requirement does not apply "if the ceiling at that airport is at least 1,000 feet above the lowest MEA or MOCA, or initial approach altitude prescribed for the instrument approach procedure for that airport, and the visibility at that airport is at least 3 miles".

  4. FAA, Special Pilot-In-Command Qualification Airports Revision History (14 CFR §121.445), revised May 2017, archived copy. The current list is kept in the FAA's Dynamic Regulatory System and has been amended since. Counts are ours, from the table: 93 entries with an ICAO code, 80 of them citing mountainous terrain, 73 with the effective date 06/20/90. 2

  5. EASA, Acceptable Means of Compliance and Guidance Material to Annex III (Part-ORO), consolidated version of February 2016, AMC1 ORO.FC.105(b)(2);(c), "Route/area and aerodrome knowledge for commercial operations". The same text stands in the UK CAA's regulatory library.

  6. Our measurement, from the Terrain Tiles published by Mapzen on AWS Open Data (sources), zoom 12. Samples every 250 m along 72 bearings out to 10 km from the airport's position in the register; the figure is the highest sample less the register's elevation, rounded to 10 m. A grid of samples can miss a summit, so the figures are low estimates. Paro: 4,054 m at 9.5 km to the west; 5,441 m at 29.5 km to the north, at zoom 11. Saba: 824 m at 2.25 km. Along the centreline, samples every 250 m for 10 km beyond each threshold; Toncontín's highest line of sight is 6.8% at 2.5 km beyond the threshold of runway 02, Palmerola's 0.1%. 2 3 4 5 6 7

  7. Department of Air Transport, Bhutan, AIP Bhutan, AD 2.1 VQPR Paro, 2nd edition, pages dated 1 March and 6 December 2018: elevation 2,244.479 m, runway 15/33 2,265 × 30 m; AD 2.22 §1, §4, §5.4.6, §5.4.8, §5.4.10 and §6. §5.5.2: "After departure climb initially 18 000ft on QNH maintaining visual to terrain/obstacle".

  8. Austro Control, AIP Austria, LOWI Innsbruck, edition of 1 October 2026, AD 2.22: §3.1.1.1–3.1.1.3 on familiarisation, §2.10.1 on foehn, defined there as surface wind from 100°–180° at 15–25 kt with gusts of 30–50 kt.

  9. DC-ANSP, AIP, AD 2 TNCS Saba, publication of 28 November 2024: AD 2.2, elevation 37.5 m (123 ft), VFR, remarks; AD 2.12, runway 12 401 × 18 m, concrete; AD 2.20, "Aircraft operations requires the authorization of the Netherlands Civil Aviation Authority."

  10. NAV Portugal, AIP Portugal, LPMA Madeira, valid from 1 October 2026, AD 2.20 §2.1–2.3. Landing limits: wind from 300°–010° magnetic, 15 kt with gusts to 25 kt; from 020°–040°, 20 kt with gusts to 30 kt; "Compliance with operating limitations is mandatory." The AIP declares a runway of 2,481 × 45 m, with 2,631 m available for take-off; the register's 2,777 m, from OurAirports, is the whole pavement.

  11. CAPA – Centre for Aviation, "Honduras' Palmerola Airport opens; Toncontín now limited to domestic", 10 February 2022.

  12. FAA, Notice N 8900.640, Update to the Special Pilot-In-Command Qualification Airports List, 13 September 2022: adds Comayagua (MHPR), Eilat-Ramon, and Mexico City's Benito Juárez and Felipe Ángeles airports; removes Beijing Daxing.

Codes, elevations and runway lengths in the airport cards are from the Dromopedia register, built from FAA NASR and OurAirports. Each entry’s data page names the source of every field; see also About the data.