Heathrow airport has reported a £321m ($387m) loss for the first half of the year even though passenger numbers returned to near pre-COVID levels in the period.
Chief executive John Holland-Kaye insisted that the introduction of the passenger cap has seen a "material improvement in performance since it came into place".
"Punctuality has improved, baggage performance has improved, and that shows that the difficult decisions we took two weeks ago are having the impact so that passengers can travel with confidence at Heathrow this summer," he said.
"Airline ground handler performance has been much more stable since the cap came into effect, and we have seen a marked improvement in punctuality and baggage performance."
Earlier this month, the west London airport announced it was limiting the number of passengers who can depart each day over the peak summer months to 100,000 until 11 September.
The decision led to thousands of flights being slashed on top of the tens of thousands of trips that had already been grounded in recent months amid the travel chaos, staff shortages, long security queues and baggage system breakdowns.
Heathrow's adjusted loss before tax during the first six months of 2022 was £321m, down from £787m in the same period in last year.
It attributed the improvement to a jump in passenger numbers, from 3.9 million to 26.1 million.
Fees paid by carriers also rose, but the airport said on Tuesday that this was "offset by increased costs as we invested ahead of demand".
Britain's busiest airport said a shortage of ground handlers is "the constraint on Heathrow’s capacity" as airlines struggle to replace staff let go due to the coronavirus pandemic.
The London hub estimated that airlines were lacking around 30% of ground handling staff compared with pre-pandemic, adding there had not been an increase in these workers since January.
"We estimate that airline ground handlers have no more than 70% of pre-pandemic resource, and there has been no increase in numbers since January," Holland-Kaye said.
Heathrow reported in its results that it had been "raising concerns over a lack of handler resource for nine months". It added that from late June, as passenger numbers began to soar, it had experienced a "worrying increase in unacceptable service levels for some passengers".
The CEO said the airport was busy during peak travel times, but any queues were "well managed and kept moving", adding that the "summer getaway has started well at Heathrow thanks to early planning and keeping demand in line with airline ground handler capacity".
Watch: Airline refunds: What are your rights as a consumer?