BRASILIA, April 10 (Reuters) - A Brazilian prosecutor is investigating possible corruption in Brazil's $5.4 billion purchase of 36 Gripen fighter planes from Sweden's Saab AB .
A spokeswoman for the federal prosecutors' office in Brasilia said on Friday the civil and criminal investigation will seek to determine whether there were "possible irregularities" in the contract, negotiated last year.
The spokeswoman confirmed Brazilian media reports that the prosecutor was looking at a $900 million difference between the price in Saab's initial proposal in 2009 and the final price agreed upon in October.
The Brazilian Air Force (FAB) chose the Gripen NG fighter over Boeing Co's F-18 Super Hornet, and the Rafale, made by France's Dassault Aviation SA. The first Gripens should be delivered to Brazil in early 2018, Saab has said.
The air force said in a statement that the price difference was due to exchange rate fluctuations and additions to the contract, including flight simulators and a wide-area display cockpit panel, or WAD.
The air force denied irregularities in the purchase and said it was ready to provide any clarifications needed.
Globo's G1 news service reported that the latest-generation WAD screen chosen by the air force is only used in U.S. F-35 fighters today and will be manufactured in Brazil by AEL Sistemas, a Brazilian avionics company based in Porto Alegre that is a subsidiary of Israel's Elbit Systems Ltd.
Prosecutor Anselmo Lopes has requested documents from Saab, the air force and AEL, including copies of contracts, financial reports and emails related to the fighter deal, G1 reported. Lopes has one year to complete his investigation. (Reporting by Anthony Boadle; Editing by Peter Galloway)