Ghost flights: how near-empty planes leaving Heathrow cost airlines almost $200 million in fuel during the pandemic

Airport landing slots are valuable enough that a single pair at Heathrow has sold for tens of millions of dollars. That value is also why, through the pandemic, thousands of near-empty "ghost flights" kept taking off — airlines protecting slots they had no passengers to fill.

A slot is permission to land or depart at a specific airport at a specific time. At a runway-constrained hub like Heathrow, slots are scarce enough to be worth serious money: Oman Air paid a reported £58 million (around $75 million) for a single early-morning pair bought from Air France-KLM in 2016, then a record at the time. Scandinavian Airlines separately sold Heathrow slot pairs to American Airlines for $60 million in 2015 and $75 million in 2017. Losing a slot outright, rather than selling it, is the outcome airlines go to some lengths to avoid.

The 80/20 rule, and why it backfired in a pandemic

Under the EU's slot regulation (EEC 95/93), still mirrored in UK law after Brexit, an airline must operate at least 80% of the slots it is allocated across a season or forfeit the unused ones back to the pool — the "use it or lose it" rule. It exists to stop carriers hoarding scarce capacity they don't fly, so slots can be reallocated to airlines that will use them.

That logic collapsed when COVID-19 travel restrictions cut demand to almost nothing. Rather than risk losing valuable long-held slots, some airlines kept flying scheduled routes with few or no passengers on board. Regulators moved to stop it: the European Commission suspended the 80/20 rule from 1 March 2020, and the UK went on to grant full alleviation from the rule for the summer 2021 season. A reduced 70:30 threshold was reintroduced for summer 2022 as travel demand recovered, meaning the underlying incentive to fly a route empty — rather than lose the slot — never fully went away.

How many ghost flights actually happened

Figures obtained from the UK Civil Aviation Authority under a Freedom of Information request classify a "ghost flight" as a scheduled or chartered passenger flight — including flights serving North Sea oil rigs — with a load factor of 10% or less. Between March 2020 and September 2021, UK airports recorded 14,472 such flights.

The monthly pattern tracks the pandemic closely. March 2020 — the month the UK went into its first lockdown, and before the 80/20 waiver took effect — produced the single highest month, with 1,772 ghost flights. A second, smaller peak followed in autumn 2020 as some services resumed with passenger demand still far below capacity.

No single airport came close to Heathrow. Of the 14,472 total, Heathrow accounted for 4,910 — a third of the UK-wide count — against 1,548 at Manchester and 1,044 at Gatwick. Scale matters here: Heathrow handled roughly 80.9 million passengers in 2019, so even a small residual share of scheduled long-haul routes running near-empty adds up to a large absolute number of ghost flights.

Working out the fuel bill

The CAA data records flight counts, not fuel spend, so the cost below is a modelled estimate, not an official figure — the arithmetic is shown so it can be checked. Jet fuel was priced at roughly $0.95 per litre in early 2022, and jet fuel weighs about 0.81 kg per litre. A Boeing 787-9 — a common type on Heathrow's long-haul routes — is estimated to burn in the region of 5.77 kg of fuel per kilometre (published cruise-fuel figures for the type range roughly 5.3–6.3 kg/km depending on stage length and payload, so this sits within the normal range rather than at either extreme).

Converting that to cost: 5.77 kg/km ÷ 0.81 kg per litre × $0.95 per litre ≈ $6.77 of fuel per kilometre. Ghost flights still fly their planned route, so both legs count; assuming an average return distance of 6,000 km gives a fuel cost of roughly $40,600 per flight. Multiplied by Heathrow's 4,910 ghost flights, that comes to just under $200 million spent on fuel for flights carrying few or no passengers. Applying the same assumptions across all 14,472 ghost flights recorded UK-wide over the period implies a total fuel bill in the region of $538 million.

A single Heathrow slot pair has sold for as much as $75 million — which is close to what airlines are estimated to have burned in fuel keeping empty planes in the air out of that one airport alone.

What about the emissions?

The same flights also burned carbon for no transport benefit. Applying an industry-average emissions figure of about 90 grams of CO2 per passenger-kilometre — the rate the International Council on Clean Transportation calculated for global passenger aviation in 2019 — to the average ghost-flight distance gives a modelled total of a little over 7,000 tonnes of CO2 for all UK ghost flights over the period. That figure should be read as a lower-bound, passenger-weighted estimate rather than the full climate cost: it is built from a per-passenger rate, whereas an aircraft burns close to the same amount of fuel whether it is carrying ten passengers or two hundred. Analyses that instead model full aircraft fuel burn for the same dataset have put total emissions from the 14,472 UK ghost flights considerably higher, in the region of hundreds of thousands of tonnes of CO2 — a reminder that "empty plane" emissions estimates vary enormously depending on whether they are counted per passenger or per aircraft.

Have ghost flights stopped?

Not entirely. The full waiver from the 80/20 rule applied through the summer 2021 season; UK regulators then reinstated a reduced 70:30 usage threshold for summer 2022 as passenger demand recovered. Airlines still had to fly 70% of an allocated slot to keep it, which — on quieter routes — can mean the same underlying calculation that produced ghost flights in 2020 and 2021 persists at a smaller scale, just with a lower bar to clear.

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