 The Pullman B @-@ 29 flew in to Muroc on 20 February 1944 , and testing began on 28 February . Twenty @-@ four drops were carried out before tests were discontinued so that improvements could be made to Thin Man . The bombs failed to release immediately , frustrating calibration tests . In what turned out to be the last test flight of the series on 16 March , a Thin Man was prematurely released while the B @-@ 29 was still en route to the test range and fell onto the bomb bay doors , severely damaging the aircraft . The modified glider mechanisms had apparently caused all four malfunctions , because of the weight of the bombs , and were replaced with British Type G single @-@ point attachments and Type F releases used on the Lancaster to carry the 12 @,@ 000 @-@ pound ( 5 @,@ 400 kg ) Tallboy bomb . 
