Airbus has already been feeling pressure from governments about A400M airlifter’s delivery delays tactical capabilities, but the loss of one of the production aircraft near Seville on May 9 looks set to further compound the problems.

Four Airbus Defense & Space personnel died when A400M MSN23 crashed onto agricultural land north of Seville’s San Pablo Airport. The aircraft—which had just come off the production line—had undergone extensive ground testing and was making its maiden flight when it suffered technical problems shortly after takeoff.

As the crew attempted a return to the airport, they managed to avoid an industrial area, but the aircraft struck power lines, caught fire and hit the ground.

Both test pilots and two flight engineers perished, but two other engineers were pulled from the wreckage by nearby farmers and are being treated for serious injuries.

The accident could not have come at a worse time for Airbus Defense & Space, which has faced heavy scrutiny over the airlifter program this year. Pressure on the company, most notably from the German government, forced a major management reshuffling, and Domingo Urena-Raso—who had overseen the aircraft’s development since 2009—was forced to resign from his post at the end of January.

Airbus replaced Urena-Raso with Fernando Alonso, who had previously overseen the A350 and A380 test programs. Alonso is now running the military aircraft business and acting as the A400M program’s new director.

He has faced challenges in getting the project back on track. The development of new capabilities through the so-called Standard Operating Clearances (SOC) process is about a year behind schedule, and deliveries of aircraft have also been delayed.

Airbus has said that the aircraft’s military capabilities—including aerial delivery, cargo-handling systems, self-defense systems and air-to-air refueling using wing-mounted pods, to be delivered as part of SOC1.5—will be integrated in the second half of 2015, almost a year later than scheduled.

However, the accident should not have a strong impact on the development of the SOCs, as Airbus was able to restart development flight trials on May 12 using other A400M prototypes. One of them, MSN4, was flown from Toulouse to Seville with Alonso onboard to demonstrate confidence in the aircraft and to boost the morale of the workforce.

The accident could have severe consequences for the delivery schedule, though. Two days after the crash, the Spanish defense ministry withdrew Airbus’s permit to fly production aircraft being prepared for delivery, potentially impacting delivery schedules, since each aircraft has to undertake a number of shakedown flights before handover to customers.

It is unclear when the Spanish authorities might reinstate the permit.

“We cannot rule out any hypothesis in the crash of the A400M,” Spanish Defense Minister Pedro Morenes told a national radio station on May 12.

“By prudence and until we know the outcome of the investigation, we will fly no A400M airplanes that are in test,” he added.

There have been suggestions that the Spanish have overreacted to the accident and that the approach of halting flight tests may be politically motivated, as the country’s voters are scheduled to go to the polls toward year-end. In the past, military aviation accidents have prompted the Spanish authorities to cancel major public airshows.

Germany, Malaysia, Turkey and the U.K. have suspended flights of the A400M until more details emerge about the cause of the accident. France, however, has said it will continue to conduct limited operational tasks with its fleet of six aircraft.

Both the flight data and cockpit voice recorders were recovered from the aircraft’s wreckage on May 10 and, despite being examined by a joint team from the Spanish ministries of development and defense, the Spanish authorities have decided to hand over the recorders to French air accident investigation agency BEA to extract and analyze the data.

Several reports have suggested that as many as three of the aircraft’s four engines failed during the A400M’s departure from Seville, so it is likely that the investigation into the cause of the accident will  focus on the fuel system.. Industry sources have stated that the fuel supply to the engines was cut off; the reasons why are unclear, but it may have been related to a software issue.

The same sources have stated that there is an override function that could have reinstated the fuel flow, but it has not been determined whether the crew tried to activate this function and it did not work, or if they did not try to do so.

With Amy Svitak in Paris and Jens Flottau in Frankfurt.