Use It or Lose It: The 80/20 Airport Slot Rule, Explained

The 80/20 rule, often called “use it or lose it,” says that an airline must operate a series of airport slots at least 80% of the time to keep them for the same season the following year. Fall below that line and the slots can go back into a pool for other airlines. It applies at busy, slot-coordinated airports, where take-off and landing times are rationed.

In the winter of 2021–22, the rule made headlines for an odd reason. Lufthansa said it faced 18,000 extra flights across its Lufthansa and Brussels Airlines brands that winter season, flown only to keep its slot rights. Critics had a name for flights flown to protect slots rather than carry people: ghost flights. (Fortune)

So why would a rule push airlines to fly near-empty planes? And is it still in force? Here’s the short version.

What is the 80/20 slot rule?

At a slot-coordinated airport, an airline doesn’t own its take-off and landing times. It is allocated them, season by season, as a series: a run of slots at the same time, repeated through the season. (If slots are new to you, start with our plain guide to airport slots and the schedule.)

The reward for using a series is historic precedence, sometimes called “grandfather rights”: a claim to the same series in the next equivalent season, summer to summer or winter to winter. Switzerland’s slot coordinator summarises the condition: “at least 80% of the slots were operated by the airline as cleared by the coordinator.” (Slot Coordination Switzerland)

The “20” is the slack. It’s room for the cancellations any airline has.

How does the 80/20 rule work in practice?

A few dates and definitions do most of the work. Under the Worldwide Airport Slot Guidelines (WASG), as summarised by Switzerland’s coordinator:

• The baseline. What an airline holds on 31 January (for summer) or 31 August (for winter) is what gets measured.
• The return deadline. Series an airline won’t fly should be handed back by 15 January (summer) or 15 August (winter).
• Late cancellations count. “All cancellations made after the Historics Baseline Date are considered as non-utilization.”
• Some misses are excused. Non-use can be justified for causes outside the airline’s control, such as an airport or airspace closure or severe weather, and for industrial action that stops the flights operating as planned.

(Slot Coordination Switzerland)

The incentive is clear: give back what you won’t use early, so someone else can have it, and fly what you keep.

Where does the 80/20 rule apply?

At slot-coordinated (Level 3) airports around the world, following the WASG; we mapped how many there are in the 2026 slot picture. In the European Union, the rule sits in the EU Slot Regulation (Regulation 95/93): in the European Commission’s words, “airlines must use 80% of their allocated slots or risk losing them in the following years.” (European Commission)

The US has its own version: the FAA sets a minimum slot-usage requirement at New York JFK, LaGuardia and Washington Reagan National, and describes “the 20 percent non-utilization allowed under the minimum usage requirement.” (FAA, via Federal Register)

What happened to the 80/20 rule during COVID?

When the pandemic emptied the skies, keeping an 80% rule would have meant flying empty planes on a vast scale. So regulators relaxed it, then brought it back in stages. In the EU:

• Summer 2020: the regulation was waived completely, and the full waiver was extended to winter 2020/21. (Mondaq)
• Summer 2021: airlines could hand back up to half their slots, and had to use at least 50% of the rest. (European Commission)
• Winter 2021/22: still 50%. Summer 2022: 64%. (Fortune, Aviation Week)
• Winter 2022/23: 75%. From summer 2023: the standard 80% requirement was set to apply again. (Aviation Week)

What are ghost flights?

“Ghost flights” are flights operated mostly or entirely to protect slots, not because passengers need them. The Lufthansa row in early 2022 showed how contested the idea is. The airline blamed the European Commission for the 18,000 flights; Commission officials told Fortune that demand wasn’t the problem and suggested ghost flights were a “scapegoat.” Ryanair’s Michael O’Leary went further: “Lufthansa loves crying crocodile tears about the environment when doing everything possible to protect its slots.” (Fortune)

That argument is the rule’s central tension in miniature. Set the bar too high in a crisis and airlines fly planes nobody needs. Set it too low and scarce slots sit idle while other airlines wait for them.

Is the 80/20 rule in force in 2026?

In the EU, yes. The 2022 legislation set the standard 80% requirement to apply again from the summer 2023 season, and the European Commission describes the 80% rule as the rule today. (Aviation Week, European Commission)

In New York, there’s still relief, for a different reason. The FAA has extended a limited waiver at JFK and LaGuardia (and for Reagan National flights to or from them) through 30 October 2027, because the New York air traffic control facility that handles those airports is short of controllers: 129 certified controllers against a target of 226, or 57% staffed. Carriers can return up to 10% of their slots at JFK and at LaGuardia. The FAA also said it does not anticipate further broad relief beyond summer 2027. (FAA, via Federal Register)

Why do critics want the rule changed?

Both sides have a case, and you can hear it in how the industry argued in 2022. As the EU set its winter 2022/23 level, IATA pushed for a lower 70/30 rule, warning that anything higher than 70% could mean operating flights demand may not justify. Airports’ body ACI World wanted the 80/20 rule back in full. (Aviation Week)

The FAA put the defenders’ view in one line: access to New York’s airspace “is a scarce and valuable public asset,” and airlines and airports should be making the most appropriate use of it. (FAA, via Federal Register)

Counting to 80

Whether a series clears 80% comes down to plain arithmetic over the schedule: which flights were planned on that slot, which operated, and which were cancelled in time. That’s why the slot book and the schedule have to agree. Holding the schedule side of that picture, flight by flight and season by season, is what SSIM Toolkit does, locally on your machine.

Sources

• Slot Coordination Switzerland — Season planning (WASG summary)
• Fortune — Lufthansa, Ryanair and the EU’s ghost flights row (13 January 2022)
• Aviation Week — European lawmakers set winter slot threshold at 75% (10 October 2022)
• European Commission — Slots (the Slot Regulation and the 80% rule)
• European Commission — Aviation: slot relief enacted (16 February 2021)
• Mondaq — Amendments to EU slot regulation cast struggling airlines a lifeline
• FAA — Staffing-related relief at DCA, JFK and LGA, Winter 2026/2027 and Summer 2027 (Federal Register 2026-12593, scheduled for publication 23 June 2026)