KLM cancelled 20 flights on Friday 23 October because of strong winds over the Netherlands, and planned another 22 cancellations for Saturday, a spokesperson for the airline said. That makes 42 flights in two days1. Amsterdam Schiphol, which typically handles more than 1,000 flights a day at this time of year, said the wind had so far had little impact on its operation. No other airline cancelled flights because of the weather, and Eindhoven and Rotterdam The Hague airports reported no cancellations on Friday1.

Storm Austen, followed by Boelo

The wind came from Storm Austen. It made landfall in Brittany on Friday morning, where local weather stations measured gusts of up to 160 km/h, and the Met Office issued an amber warning for Cornwall and Devon, where gusts reached 130 km/h2. Austen reached the Netherlands from the southwest on Friday afternoon. The Royal Netherlands Meteorological Institute (KNMI) issued a code yellow warning for South Holland, Zeeland, North Brabant, Limburg, Gelderland and Overijssel, with gusts of 75 to 90 km/h expected in coastal areas and the southeast2. The warning ran from 19:00 on Friday to 09:00 on Saturday, and gusts of 70 km/h had already been measured in Zeeland on Friday afternoon3.

A second storm, Boelo, was forecast to arrive from the north of the United Kingdom on Saturday, with a code yellow warning for the far north of the country on Saturday evening and night4. Several events were called off and ferry services to the Wadden Islands were reduced for the weekend1.

What the Schiphol data shows

At Schiphol itself, the wind stayed moderate on Friday. The airport's routine weather reports (METARs) show a southeasterly wind of 14 to 18 knots for most of the day, with a highest gust of 28 knots at 08:55 local time5. That allowed Schiphol to land traffic on runway 18R, the Polderbaan, and on runway 18C for most of the day, according to ADS-B data from KLM aircraft that we analysed via adsb.lol6.

Around 16:00 local time the wind backed to the east. The 16:25 report gives a wind from 100 degrees at 16 knots, gusting 26 knots5. Runway 18R has a true bearing of 183 degrees7, so that wind blew almost straight across it. Our own calculation puts the crosswind component at 16 knots, and just over 25 knots in the gusts. On runway 06, the Kaagbaan, with a bearing of 58 degrees, the same wind gives 11 knots, or 17 knots in the gusts75. The last KLM arrival in our sample to use 18R landed at 16:26; the first to use runway 06 touched down a quarter of an hour later6. From 18:46, after the wind had swung round to the north, arrivals were landing on runway 36R65. Across 160 landings by 91 KLM aircraft up to 19:00 local time, the ADS-B tracks show no go-arounds6.

A go-around in Brussels and a diversion to Amsterdam

In Belgium, where several provinces were under a code orange warning, the wind was much stronger8. At 15:20 local time, Brussels Airport reported a southerly wind of 25 knots gusting 35 knots, with wind shear reported on runway 19. Half an hour later the wind was 31 knots, gusting 42 knots9. A Brussels Airlines Airbus A319 (OO-SSW) arriving from Marseille was on final approach to runway 19 at that time. About 6 km from the airport, at 15:30, the crew discontinued the approach and climbed away10. The aircraft then flew north and landed on runway 18R at Schiphol at 16:07. It departed again at 18:06 and arrived in Brussels at 18:3010. NOS also reported that a flight from Marseille to Brussels was diverted to Schiphol8.

Crosswind limits and Schiphol's runway system

Aircraft take off and land into the wind wherever possible, so wind direction and speed determine which runways air traffic control can offer. At Schiphol, the primary take-off and landing runways are selected with a crosswind criterion of 20 knots11. A secondary runway may have more crosswind, but accepting it is explicitly the pilot's responsibility11. Gusts of less than 10 knots above the mean wind are not taken into account7. Each aircraft type has its own limits, and for many types the maximum is around 30 knots12. Under the certification rules for large aeroplanes, a manufacturer must demonstrate safe take-off and landing with a 90-degree crosswind of at least 20 knots, or 0.2 times the stall speed in the landing configuration if that is higher, though the demonstration need not exceed 25 knots13. Airlines and individual pilots can apply stricter limits on top of that14.

In a moderate southwesterly wind, the Polderbaan is the main landing runway. If the wind veers further or strengthens, it eventually falls outside the crosswind limit for a main landing runway. Runway 09/27, the Buitenveldertbaan, then takes over that role, and the Polderbaan becomes a secondary landing runway for pilots who accept the crosswind. With even more crosswind, the Buitenveldertbaan remains as the only landing runway14. Schiphol uses runway 09/27 for landings in westerly winds and can add runway 04/22 in stormy southwesterly conditions15. During inbound peaks two landing runways are normally in use7. When only one is available, LVNL limits the flow of arriving traffic to match it14. Airlines with an agreement with LVNL can be exempted from that regulation if the pilot accepts the crosswind on the secondary runway before departure; if landing there is not possible, the aircraft diverts to its alternate714.

Cancelling in advance versus go-arounds and diversions

Cancellations are a planning decision on the ground: an airline removes flights when fewer arrivals and departures are possible than its schedule requires. A go-around and a diversion are decisions taken by the crew in the air, when a landing is not safe or not possible at that moment. Air traffic control at Schiphol may also deviate from the preferred runway sequence when wind shear is reported near the airport7. Read more about when and why pilots fly a go-around.

Passenger rights under EU 261

When a flight is cancelled, Regulation (EC) No 261/2004 gives passengers the choice between a refund and rerouting to their final destination16. The airline must also provide meals and refreshments, and a hotel with transport when an overnight stay becomes necessary16. Financial compensation is not due if the airline can prove that the cancellation was caused by extraordinary circumstances that could not have been avoided even if all reasonable measures had been taken16. The recitals of the regulation name meteorological conditions incompatible with the operation of the flight as an example of such circumstances16.

Practise wind and runway questions

Working out crosswind components, decoding a METAR and understanding how an airport selects its runways all come back in the ATPL theory exams. Practise with ATPL Meteorology and ATPL Operational Procedures. Interested in flying for the airline itself? See the KLM airline profile and practice for the KLM Flight Academy selection.