Passengers flying from Stansted are being advised to contact their airlines after flights were disrupted by eco-protesters.
Services are returning to normal after 52 outbound and inbound Ryanair flights were cancelled, but delays are still possible.
Police made 57 arrests after protesters from climate action group Plane Stupid broke through the perimeter fence and occupied a secure area near the runway.
Some of them chained themselves to fencing they had dragged into the area.
The runway was shut for about two hours and reopened at 8.10am, five hours after the protest started.
Ryanair has demanded an investigation into the incident, which has raised concerns over security at the Essex airport.
Stansted divisional police commander Ian Gruneberg said he was concerned that the protesters had managed to cut through the perimeter fence.
"It is a matter we will be reviewing with the airport," he said.
But BAA's commercial director at Stansted, Nick Barton, defended security at the airport. "The protestors were unable to get to the runway," he said.
"Bear in mind that the runway is about 2,000 acres in size and we don't intend to run an airport as a fortress."
Plane Stupid is opposed to BAA's plans to extend capacity at Stansted and Heathrow. Protester Lily Kember said: "Climate change is a global catastrophe in the making."
To check the status of your flight, visit www.stanstedairport.com.
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