Original sentence: It was originally intended to be a glider.It was subsequently  used for low speed research in support of the Concorde development programme while the BAC 221, (a modified Fairey Delta 2) covering high-speed research.The single aircraft XP841  flew for first time on 17 August 1961 at the Royal Aircraft Establishment with J.They intended to use a Canberra aircraft to tow it to high altitude of around 30,000 ft (9,140 m).They looked at the costs involved in this and estimated that a powered version would achieve 200% more flying time at 95% less cost per hour
Edited sentence: After reviewing costs, it was estimated that a powered version would achieve 200% more flying time at 95% less cost per hour.It formed part of the British supersonic aircraft research programme sponsored by the Ministry of Supply that eventually emerged as the Concorde.It was originally intended to be a glider, being towed by a Canberra aircraft to high altitude of around 30,000 ft (9,140 m).It was subsequently  used for low speed research in support of the Concorde development programme while the BAC 221, (a modified Fairey Delta 2) covered high-speed research.The single aircraft XP841  flew for first time on 17 August 1961 at the Royal Aircraft Establishment Bedford, with J