A further short flight was made on 20 January before an endurance flight, starting at 09:38 on 27 January when R100 slipped the mast at Cardington and ending at 15:26 on 29 January after more than 53 hours in the air. Following this flight, it was returned to the shed for work on the cover to be carried out. At the same time, the original reconditioned Condor IIIA engines were replaced by six new Condor IIIBs and some weight was eliminated by reducing the amount of passenger accommodation. The work was complete by the end of April, but on 24 April it was caught by a gust while being walked out of the shed, damaging the tail surfaces. The wind prevented it being replaced in the shed, so it was moored to the mast. It was not possible to return it to the shed for repairs until the morning of 27 April. Repairs took longer than expected, and R100 remained in the shed until 21 May, when it made a 24-hour flight intended to test the new engine installation and modifications to the cover.