Gatwick Airport's South Terminal was evacuated on Friday, 22 November, while a "security incident" was investigated.
Footage showed crowds gathering outside the building while they were unable to enter the terminal as investigations were carried out.
There are fears flights will consequently be disrupted, causing travel chaos.
On Friday morning, Gatwick officials said they were working to resolve the issue as quickly as possible.
“Passengers will not be able to enter the South Terminal while this is ongoing," a statement read.
