A number of inbound flights were diverted to Glasgow after a suspicious package was found in the search area of Edinburgh Airport. A number of outbound flights have also been cancelled.
The airport was evacuated and a police cordon set up after the discovery of a "potentially suspicious bag" at 1.50pm.
Bomb disposal experts are on the scene.
Some passengers congregated on a nearby car park while others were moved to a nearby hotel.
Police have urged others not to travel to the airport.
A Police Scotland spokesman said: "Police at Edinburgh Airport have implemented a closure of the building and the access roads following the discovery of a potentially suspicious bag within the central search area at around 1.50pm today.
"The Explosive Ordnance Disposal are currently in attendance to inspect the item and officers are maintaining a cordon to ensure the safety of the public."
A Scottish Government spokeswoman said the First Minister, Deputy First Minister and Justice Secretary are aware of the incident and the government's resilience operation has been activated.
She said: "Police Scotland are in operational charge of the situation and continue to update ministers on a regular basis."
EasyJet, which has had flights from Munich and Berlin diverted to Glasgow Airport, told customers the situation could take up to three hours to be resolved.
The airline tweeted: "The local authorities at Edinburgh airport have assessed the situation and estimated a minimum of 2-3 hours until the issue will be resolved.
"We advise all passengers to regularly check our flight tracker for any updates and the status of your flight."