The federal prosecutor's office said the individuals were seized in sweeps which began on May 12 in Zurich and Basel, following an investigation which revealed that their cell had "very seriously considered" attacking the Israeli carrier in Switzerland.
The office did not reveal the individuals' names or nationalities, but said law enforcement agents in other European countries, including France and Spain, had played a part in the investigation.
According to unconfirmed media reports, the El Al plot involved shooting down a plane at Geneva airport during landing or take-off, from outside the airport perimeter.
Philippe Roy, spokesman for Geneva airport, told AFP that El Al had halted flights to the Swiss city for a week last December, officially for "commercial or technical" reasons.
The carrier's flights were instead routed to Zurich.
The Swiss prosecutor's office said that investigators uncovered the plot here after police identified a gang of around a dozen members early in 2005.
Some of the money gained by the gang members through a series of robberies in Zurich and elsewhere in Switzerland ended up in the hands of a terrorist group, the office said.
The gang also had links with similar cells in France and Spain.
One member of the Swiss cell had also been in contact with Mohamed Achraf, a North African suspected Islamist extremist who was arrested in Switzerland in 2004 on unrelated immigration charges and extradited to Spain in April 2005 for allegedly plotting to bomb Spain's highest court.
In November 2002 an attack on an Israeli plane involving two shoulder-fired missiles launched at an Arkia plane in Mombasa, Kenya, narrowly missed the aircraft carrying 261 people.
The attacks attempt was claimed by Osama bin Laden's Al-Qaeda network.