 Cost estimates doubled from $4 billion to $8 billion and production slipped from 2017 to 2020, then grew to $10 billion for life extension plus $1 billion for tail guidance kits and production was delayed to 2021.Sequestration budget cuts in early 2013 delayed any start until 2020.The Senate Energy and Water Appropriations Subcommittee stated that extending the life of B61s and consolidating its variants may not be a cheap and low-risk method to meet military requirements.