EgyptAir plane
EgyptAir plane Reuters

A baggage handler or airport worker at Paris's Charles De Gaulle International Airport could have planted a bomb on doomed EgyptAir flight MS804, French investigators announced overnight Sunday/Monday - but the airport will not boost its security. 

One airline desk officer confirmed to the British Telegraph that airport security "sometimes" performed spot checks on airport staff, but could not guard every door due to budgeting concerns. 

But this is already a step up from typical airport procedure prior to the Islamic State (ISIS) attacks on Paris in 2015, after which Charles De Gaulle already upped security. Since then, the airport has checked 86,000 workers and fired 60 due to links with Islamism - but won't boost security further, an airport spokesperson said.  

Tragedy

The Airbus A320 carrying 56 passengers and 10 crew and security officers disappeared over the Mediterranean as it flew from Paris to Cairo. It was flying at 37,000ft when it disappeared from the radar at 2:29 a.m.

International air and naval teams discovered debris of the plane Friday, 180 miles (290 kilometers) north of Alexandria. Among the wreckage were personal belongings of passengers and crew. 

However, Egyptian authorities revealed the plane emitted emergency signals some two hours later. At around the same time, sailors in a ship in the Mediterranean claimed they saw a massive fireball streaking through the sky.

Egypt's civil aviation authority confirmed a mid-air explosion had occurred, and after initially saying they weren't ruling any causes out admitted that a terrorist attack was more likely the cause than a technical failure.

Retracing steps

Meanwhile, French authorities have also focused on the last flights MS804 took before plunging into the sea, the Wall Street Journal reports.  

The EgyptAir plane carrying MS804 flew from Cairo to Brussels and back on Tuesday, then to Eritrea. On Wednesday, it flew one round trip from Cairo to Tunis and back before heading to Charles De Gaulle, before making the fatal flight early Thursday. 

Analysts note that four out of five of the airports the plane stopped at during this journey are under heightened security measures due to recent terror attacks: Brussels, Tunis, Paris, and Cairo. 

As such, authorities are scrutinizing the hundreds of workers who could have had access to the plane at each airport and stop. 

The plane itself swerved erratically just after entering Egyptian airspace, following an odd path for over an hour before crashing. 

But while there are some indications that may point to an onboard fire - including several messages sent out by an automated warning system in the final moments before the explosion - the exact cause remains a mystery until the plane's crucial black boxes are found.