Early on, Air Chief Marshal Arthur Harris, head of Bomber Command, was scathing in his criticism of the Halifax's performance in comparison to the new Avro Lancaster, primarily of its bomb-carrying capability: an average Halifax was calculated to drop 100 tons of bombs in its lifetime, compared to a Lancaster's 154. Harris continued to have a poor opinion of the Halifax, despite the fact that later Hercules-engined machines had lower loss rates and higher crew survival rates after abandoning the aircraft than Lancasters, and came very close to the Lancaster's speed and altitude performance. The Halifax was progressively outnumbered in front-line service over occupied Europe as more Lancasters became available from 1943 onwards; many squadrons converted to the Lancaster.