A400M black box sent to U.S. to seek crash clues - sources

PARIS/BERLIN, May 18 (Reuters) - Spanish officials investigating the fatal crash of an A400M military plane have sent at least one of its 'black box' flight recorders to the United States after problems in reading the data, people familiar with the matter said.

The Airbus Group troop and cargo plane crashed shortly after takeoff outside Seville on May 9, killing four crew and injuring two others.

Voice and data recorders were quickly retrieved and sent to France to be analysed, but compatibility problems hindered the process off downloading data.

At least one of the boxes has been sent to Florida to be analysed using specialist equipment at the manufacturer, L3 Communications, the people said.

Airbus Defence & Space declined to comment.

The Spanish defence ministry, which is leading the investigation, has declined all comment on the probe.

The crash prompted four nations to ground the plane and France to limit its use to essential operations.

Spain also withdrew permission for flight tests, effectively halting deliveries.

"We are reviewing the delivery schedule ... and waiting to hear the results from the investigation," an Airbus spokesman said.

Airbus has delivered two A400Ms this year and had planned on building and delivering a further 12.

For now, production at the Seville assembly plant is unaffected by the halt in deliveries, the spokesman said. (Reporting by Tim Hepher, Sabine Siebold, Sonya Dowsett, editing by David Evans)