Have you been eyeballing the Flightradar24 list of most tracked flights during European morning hours for the past couple of weeks? Then you’ve probably noticed how quite a few flights have ended up holding around Kraków’s John Paul II International Airport (KRK/EPKK). The culprit? Fog.
Kraków Airport is perfectly located for fog formation
Kraków Airport’s location makes it particularly susceptible to fog formation. The airport lies in a natural basin where cold air settles and accumulates, especially during calm overnight periods. This geographical feature, combined with the proximity to the Vistula River and surrounding wetlands, creates the perfect recipe for fog development.
When the sun sets and temperatures drop, moisture from these water sources condenses in the cooler air trapped in the valley. The result is dense fog that can blanket the airport well into the morning hours, significantly reducing visibility for pilots during critical takeoff and landing phases.
Why mornings are most affected
Radiation fog, the type most common at Kraków, typically forms during clear, calm nights when the ground rapidly loses heat. This process intensifies in the hours before dawn, meaning that early morning flights are most likely to encounter poor visibility conditions.
Temperature inversions compound the problem. A layer of warmer air settles above the cold, fog-filled air in the valley, acting like a lid that prevents the fog from dissipating. Even after sunrise, it can take several hours for the sun to heat the ground enough to break through this inversion and clear the fog.
Seasonal patterns
While fog can occur year-round at Kraków, certain seasons are particularly problematic:
- Autumn: Warm days followed by cool nights create ideal conditions for fog formation
- Spring: Similar temperature fluctuations lead to frequent morning fog
- Winter: Though less common than autumn, winter mornings can still see significant fog events. This winter has been no exception.
Different ILS categories
Kraków Airport is equipped with an Instrument Landing System (ILS), however only a Category I ILS. This limitation makes KRK particularly vulnerable to fog and low visibility conditions. To understand why, we need to break down the different varieties of ILS categories:
CAT I ILS: Allows landings with a decision height of 200 feet and runway visual range of at least 550 meters. This is what Kraków currently offers.
CAT II ILS: Permits operations down to 100 feet decision height and 300 meters visibility.
CAT III ILS: Enables landings in near-zero visibility conditions, divided into three subcategories:
- CAT IIIA: Decision height below 100 feet (typically 50 feet or no decision height) with runway visual range of at least 200 meters.
- CAT IIIB: Decision height below 50 feet (or no decision height) with runway visual range between 50 meters and 200 meters, or no decision height with RVR less than 200 meters but not less than 50 meters.
- CAT IIIC: No decision height and no runway visual range minimum—truly zero-visibility operations with completely automatic landings. However, this is more of a theoretical, “future-proofed”-category as there are no CATIIIC approaches currently in use (to my knowledge, feel free to correct me if I’m wrong in the comments below).
The absence of CAT II or CAT III capabilities at Kraków means that when fog reduces visibility below CAT I minimums, which as we have noticed have happened regularly during the fall and early winter, aircraft simply cannot land. This regardless of how sophisticated their onboard equipment might be. Instead, traffic often ends up diverting to nearby Katowice (KTW/EPKT) or Warsaw (WAW/EPWA)—that offers CATII, respectively CATIIIA.
How Kraków airport is addressing the fog issue
The cost of installing, certifying and maintaining a more capable level of Instrument Landing System is hardly pocket change for the operator of Kraków Airport. That said, the Polish Air Navigation Services Agency (PAZP), did in fact announce a public tender for the construction of a CATII capable approach system already a year ago.
Lowering the decision height and visibility requirements probably would alleviate some of the fog related issues. By the end of the day, investment in CATIII capability is ultimately what the airport is in sore need of. And for that to be possible, a completely new runway would have to be constructed. As luck has it, that is also in the works for Poland’s second busiest airport.
Travelers will just need to wait until at least 2029 for that to become a reality.
