The EgyptAir plane that crashed in the Mediterranean had flown through five airports in the 48 hours before it disappeared off radar screens. As authorities try to determine what went wrong, here's a look at airport security and safety at those five sites:

PARIS

The plane's last stop was Paris' Charles de Gaulle Airport, the second-biggest in Europe and the ninth in the world for passenger traffic. Of its 100,000 employees, thousands are border police officers, customs personnel, soldiers and private guards who patrol daily to secure public areas, baggage sorting sections and tarmacs.

French authorities increased random security checks, video surveillance and sniffer dogs at the three Paris airports after last year's deadly extremist attacks. Scores of staff members had badges revoked amid suspicions of radicalism. The foreign minister and transport chief insisted Friday that airport security is at the highest possible level.

CAIRO

The Airbus 320 had arrived in Paris from Cairo, the hub for EgyptAir. The crash is the third plane incident involving Egypt in eight months and renewed security concerns surrounding Egyptian planes and airports.

TUNIS

Before Paris, the plane made a round-trip to Tunisia's capital, whose airport sees 5.5 million passengers a year. Tunisian authorities have increased security repeatedly since Islamic extremist attacks on a museum and a beach killed dozens of foreign tourists in 2015. They have added explosives detection abilities and more staff to inspect baggage, and held an international airport security audit. The country is facing a growing threat from Islamic State extremists from neighboring Libya and within Tunisia.

ASMARA

The EgyptAir plane also made a round-trip flight to the capital of the African nation of Eritrea. The Asmara airport has just two runways, and is shared with the Eritrean Air Force. The U.S. Office of Diplomatic Security said in a report last year that Asmara airport security is "unpredictable" and noted a lack of consistency in checks by the conscripts handling airport security and lack of technology to check for fraudulent documents.

BRUSSELS

The previous round-trip from Cairo was to Brussels, where IS-linked suicide bombers attacked the airport departure hall in March attacks on the city that killed 32 people. The transport minister resigned over a leaked report citing security shortcomings in airport security oversight. The airport, which used to handle 23.5 million passengers a year, has reopened partially with extra security measures, including bag checks before entering the terminal.