Three sources familiar with the investigation said the SFO had written to former suspects to say it would take no further action. Overseas prosecutors could, however, take a different view in cases where suspects face more than one inquiry.

Airbus and the SFO, which along with French and U.S. prosecutors agreed to a ground-breaking deferred prosecution agreement (DPA) https://www.reuters.com/article/us-airbus-probe-france-idUSKBN1ZU1X4 with the company in January 2020, declined to comment.

But the SFO updated its website on April 22 to state that its case would remain open until the end of the DPA - a settlement that allows companies to avoid criminal prosecution in a court-approved deal that often includes a fine and compliance monitoring - in January 2023.

It previously stated that the inquiry remained active and the position in relation to individuals was being considered.

Airbus was accused of a "pervasive and pernicious" bribery scheme by a U.S. district judge last year after a four-year inquiry into sales across more than a dozen overseas markets culminated a corporate settlement.

Last week, the company drew a final line under British criminal investigations when former subsidiary GPT Special Project Management pleaded guilty to corruption over military contracts for Saudi Arabia.

Successfully prosecuting white collar crime is notoriously tricky, time-consuming and costly, especially if prosecutors rely on overseas authorities to share documentary evidence.

But the SFO, which has yet to successfully prosecute individuals following a DPA, has faced criticisms of serious failings after the collapse of high-profile trials against former executives at Serco, over prisoner-tagging, and at retailer Tesco after corporate settlements.

It also abandoned investigations into suspects associated with aero engine maker Rolls-Royce and drugs company GlaxoSmithKline in 2019, raising the ire of anti corruption groups that say it is absurd for companies to settle allegations of wrongdoing when individuals cannot be held to account.

But Sarah Wallace, a lawyer at Constantine Law, noted it was inherently more difficult to prosecute and secure convictions against individuals than agreeing a DPA with a company.

(Additional reporting by Tim Hepher in Paris. Editing by Mark Potter)

By Kirstin Ridley