The airport, Europe’s biggest before the pandemic, previously extended the restrictions, which had been due to end on Sept. 11. It had said it would keep the cap in place until enough staff and resources had been mobilized to prevent the long lines and persistent delays that characterized travel for much of this year.

Heathrow is one of a handful of airports that had put in place capacity restrictions—unusual in their duration and scale—to help cope with severe staffing shortages across almost every corner of the industry.

Airlines, airports and their suppliers have worked to rapidly bolster their operations after the sector was brought to a near standstill at the onset of the pandemic. A number of false starts, as travel restrictions were removed and then reintroduced with the spread of new Covid-19 variants, has impeded that recovery.

The London hub has repeatedly pointed to a shortage of ground handlers that it blamed for lines that have stretched outside its terminal doors, long waits at baggage reclaim, persistent departure delays and scrapped flights.

“This cap resulted in fewer last-minute cancellations, better punctuality and shorter waits for bags,” a spokeswoman for Heathrow said Monday. “Our focus has always been on removing the cap as quickly as possible—but we will only do so if we are confident that adding in more passengers will not erode the service levels that the cap has secured.”

While the seasonal capacity reduction will finish at the end of October, Heathrow will still have a separate restriction that prevents airlines from making changes or additions at peak periods, the people familiar with the plans said. A separate emergency measure, which can be used to limit capacity for shorter periods, will also still be available to the airport in the case of severe disruption during peak travel periods, one of the people said.

Heathrow’s cap was originally put in place in July, when the airport warned that airlines had planned to fly about 4,000 more people than it could handle each day through the peak of summer. Airlines were told to cancel passengers’ bookings, restrict sales and divert flights where possible to alternative airports to comply with the mandate.

Winter typically sees fewer travelers than in summer, with July and August marking the annual peak in flying. Still, in November 2019, Heathrow averaged about 104,000 daily departing passengers, with that figure rising to 108,000 in December, according to company statistics, both higher than the expiring daily cap. Heathrow has been operating at about 80% of 2019 levels this summer, according to the most recently available monthly figures.

Airlines have already reduced their Heathrow flying schedules over the next six months to try to limit disruption at the airport. British Airways, Heathrow’s biggest airline, said in August that it would cut 10,000 flights from the end of October through March to help manage disruption at the hub.

The move comes after Amsterdam Schiphol Airport, another critical hub in Europe, said last week it would extend its own curbs on passenger numbers through the end of March as it battles with staffing shortages, in particular of security personnel. It said it would be able to review the restrictions in January.

Write to Benjamin Katz at ben.katz@wsj.com