Abstract: A thrust reverser for a gas turbine engine (10) comprises cascade structures (20,22) mounted in an engine cowl (12). The cascades (20,22) comprise a plurality of air deflecting vanes (24) arranged in fixed space relationship. At least one of the cascades (22) translates between a first inoperative position where the cascade (22) is stowed radially inward of the cowl (12) and a second operative position where the cascade (22) is clear of the cowl (12) to expose the air deflecting vanes (24). When the trust reverser is operative blocker doors (26) pivot across an annular duct (13) defined between the core engine (11) and the cowl (12) to deflect the airflow passing therethrough to the exposed cascades (20,22) to produce a braking force.