Four people and defunct Cyprus budget carrier Helios Airways will go on trial in September over the island's worst air crash which killed all 121 people on board in 2005, according to Nicosia court.

Helios Airways and four officials face a total of 1,190 counts of manslaughter and reckless endangerment in what promises to be one of the most complex and high-profile cases in Cypriot legal history.

The five accused are Helios chief executive officer Andreas Drakos, managing director Demetris Pantazis, operations manager George Kikides, chief pilot Ianko Stoimenov and Helios Airways itself as a legal entity.

State prosecutors are charging them with manslaughter and causing death by a reckless act on the grounds that they hired "unsuitable and inadequate" pilots.

According to the prosecution, the charges are among the "most serious" provided for under the Cyprus criminal code.

The accused are being held responsible for the death of 119 of those on board - excluding the two pilots who are deemed partly to blame for the crash, which was the deadliest aviation disaster for both Greece and Cyprus.

Families of the dead have long called for criminal action against those deemed responsible for the Helios Airways Boeing 737-300 being starved of oxygen and then slamming into a hillside outside Athens in August 2005.

The plane ran out of fuel after flying on auto-pilot for several hours.

The case comes after more than three years of police investigation amid accusations by the relatives of official foot-dragging.

In October 2006, a Greek commission of inquiry said the Helios pilots had failed to recognise early warnings of a drop in cabin pressure and had omitted to switch pressurisation from manual to automatic in pre-flight checks.

Helios has strongly denied any suggestion that it cut corners in air safety, saying all its pilots were fit to fly and subject to the appropriate checks.

The main charge of manslaughter carries a life sentence, and causing death by a reckless, thoughtless or dangerous act, carries a maximum four-year prison term.

Helios was later renamed Ajet Aviation, which ceased flight operations in late 2006.