After an EgyptAir flight from Paris to Cairo crashed on Thursday, presumably killing all 66 people on board, many have questioned whether the crash was due to a terror attack.
Among them are aviation and defence experts including Egypt's own aviation minister, who said a terror attack was the “most likely” of the possible causes.
If indeed this is the case – and it's important to stress that right now all we have is speculation – it raises questions as to how terrorists could have potentially breached security at the Charles de Gaulle airport in Paris.
"We are still not sure of [the cause], but the incident has triggered a series of checks," said an expert cited in Le Figaro.
A senior official at the airport said France's air police (GTA) would be reviewing video footage and other information relating to MS 804, the French daily said.
The official added: "Investigators will inevitably be interested in the ground crew... numerous salafists have been detected in the past, among those workers who had access to areas for loading and unloading aircraft. Sometimes there is complicity in airports. We must not hide that fact."
Security was tightened at the airport in the wake of the November 13th attacks in Paris, with authorities screening all workers at the two Paris airports - CDG and Orly.
Worryingly, they decided to revoke "secure zone access" to almost 70 workers, with the head of Aeroports de Paris citing the main reason as "cases of radicalization".
Around 85,000 people have access to the secure zones, for example baggage handlers, aircraft cleaners and suppliers working for airlines or sub-contractors.
"To be issued with a red badge, you have to be cleared by police, and if you work for a company that carries out security checks of in-flight luggage, you need three police checks," said Augustin de Romanet, chief executive officer of Aeroports de Paris (ADP).
He added that deployment of military personnel at the two airports had been boosted by half following the attacks, and passport officers were checking the IDs of all people leaving the country, "including flights in the Schengen zone," the European Union's border-free area.
And after the blast at Brussels airport, security was tightened yet again. Forty extra officers, backed up by riot police, were dispatched, and passenger profiling was introduced to watch for "abnormal behaviour".
But as more information surfaces about the cause of MS804's crash, Charles de Gaulle airport in Paris, where the fated flight originated, will be under fresh scrutiny.
An EgyptAir employee answers questions at Charles de Gaulle airport. Photo: Thomas Samson/AFP
"A bomb placed on board at Roissy or in Cairo is always possible because it's difficult to make your airport 100 percent watertight, even in an airport with such tight surveillance as Roissy (Charles de Gaulle)," aeronautics expert Gerard Feldzer told AFP on Thursday.
De Romanet had said that the terror threat had been a "heavy blow" to air travel in and out of Paris and expressed hope that things would soon return to normal.
But tensions have been high and there have been numerous terror scares at the major airport; in April, passengers were left in tears after learning that there was an unidentified bag on their flight from Paris Charles de Gaulle, and that an "Arab" man had failed to board after checking in, and in March a Briton was kicked off an easyJet flight after he was found to have boarded with a penknife.
Over the busy Easter period in March, an AirFrance employee told The Local they were trying to carry on as normal after the Brussels attack. "We can't allow ourselves be scared to work in airport," they said.
But despite extra security measures being in place, some travellers were surprised at the lack of extra checks on entering the airport.
One 68-year-old British expat living in France said that while she was not worried about travel between France and the UK, "you just walk in with your bag and there's nobody stopping you or anything. I thought there would at least be people by the doors to check you."