BAE Systems has taken a step closer to removing pilots from fighter jets by launching the first major test flights for a new generation of intelligent drone aircraft.

The defence group is assessing software for unmanned aircraft that will operate with an unprecedented level of independence. Defence experts believe pilotless planes are the next progression from manned fighters such as the Typhoon jet, made by BAE.

The project, named Astraea, differs from the current drone models in use in Afghanistan, which are flown remotely by pilots on the ground. Instead the prototypes will follow a set of programmed instructions, with the aim that they could fly difficult missions autonomously for days at a time.

BAE is using a conventional aircraft – an 18-seater Jetstream propeller plane – for the flights over the Irish Sea and will have technicians on board. The Jetstream will fly autonomously during some tests but there will be a pilot at the controls at all times, ready to take over if there is a problem.

The tests will include a collision avoidance trial, using a light aircraft that will gauge the plane's ability to dodge potential hazards. A BAE spokesperson said: "This will demonstrate to regulators such as the Civil Aviation Authority and air traffic control service providers the progress made towards achieving safe routine use of UAVs [unmanned air vehicle] in UK airspace."

The test flights started at the beginning of the month and will run until September, and are taking place in controlled airspace. The Astraea programme is run by a consortium whose members include BAE and other UK companies such as Cobham, Qinetiq and Rolls-Royce. Thales, the French defence and security group, is also a member.

Edward Hunt, a senior consultant at IHS Jane's, the defence analysis firm, said the argument for intelligent, unmanned aircraft was compelling. "There are some doubts as to how many more generations of manned aircraft there might be. There could be one or two more, but you can make these planes smaller and more robust without someone onboard. Also, of course, you reduce the likelihood of losing crew."

However, Hunt said technical and legal hurdles remained. "Giving them any autonomy is going to be complicated in terms of technical developments, such as the software, and legally allowing a fighter without a human being in it to launch a weapon and kill someone," he said. BAE executives have already stated that "there has to be a man in the loop" when combat drones operate, ruling out the possibility of a computer deciding whether to take a life.

BAE has already built a number of UAV prototypes including the Mantis, for civilian missions such as rescue searches, and the Taranis, a weaponised cousin. Neither will reach the mass-manufactured stage but are being developed at BAE's Warton facility in Lancashire.

BAE expects to build widely used unmanned aircraft with France's Dassault under an Anglo-French defence pact. The project, dubbed Telemos, aims to produce an eight-tonne, twin-propeller surveillance aircraft by 2016. Underlining the plane's monitoring role, the programme is named after the Cyclops of Greek mythology that warned of an attack by Ulysses.

The drone will be designed to carry laser-guided bombs. Dassault has estimated that the companies will invest €500m (£403m).